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I LIBRARY OF CONGRESS. : 



* UNITED STATES OF AMERICA.* 

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ASTRONOMY 



WITHOUT A TELESCOPE: 



A GUIDE-BOOK TO THE VISIBLE HEAVENS, 



WITH ALL NECESSARY 



MAPS AND ILLUSTRATIONS. 



DESIGNED FOR THE USE OF SCHOOLS. 



E. COLBERT. 






CHICAGO : 
GEORGE & C. W. SHERWOOD. 

1S69. 



Entered according to Act of Congress, in the year 1869, 

By GEO. & C. W. SHERWOOD, 

In the Clerk's Office of the District Court of the United States, for the Northern District of Illinois. 



CHURCH, GOODMAN AND DONNELLEY, PRINTERS, CHICAGO. BOND AND CHANDLER, ENGRAVERS. 



OfcrJDtfP 



PREFACE. 



There are four ways of regarding a subject — with the eye of sense, of reason, of fancy, and of faith. These 
severally constitute direct, inductive, dreamy, and substituted vision. The first is in itself interesting, yet not 
complete, or always reliable ; but it is especially valuable as being the basis of all that is true in the second, 
consistent in the third, and credible in the last. 

While in other departments of scientific tuition, the eye of sense is first appealed to, the would-be student 
of astronomy has generally been first taught to use some one of the other three ; dissertations on the profundities 
. of space and the acme of complicated motion, views of elaborately engraved monstrosities, with long chapters 
from the heathen mythology, and obscure descriptions of the invisible ; all these, instead of a simple delineation 
of the heavens, as visible to the naked eye. It is thus that astronomy, naturally pleasing, and normally useful, 
is a sealed book, except to the select few — a general ignorance due altogether to the lack of aid to the study. 

The following work is intended as an introduction to an acquaintance with the visible heavens ; to educate 
the eye into an ability to recognize the most prominent stellar groups. The maps are small and simple ; they 
present, in usable form, all the star groupings ordinarily visible to the naked eye in the United States, showing 
them, with little distortion, in the same relative positions as they occupy in the firmament, and without cumber- 
ing them up with painted figures — the form of the constellation is given only in faint outline. The greater 
portion of the maps are projected on the ecliptic as a base line, enabling the student to refer each star directly 
to the earth's path, and to trace out readily the course of a planetary body. The maps are so connected that 
a transition from one to another is easy, and the necessary explanatory text lies in, or near, the same opening 
of the book as the matter explained, while conciseness is aimed at throughout. 

The solar system is treated visually and deductively. No attempt has been made to describe positions or 
appearances inappreciable to the naked eye, except so far as they are necessary to a proper comprehension of 
that which can be seen by the unassisted vision. The phenomena of the heavenly motions are explained, and 
concise aids are furnished for determining, almost at a glance, the positions of the principal members of the solar 
family among the fixed stars, and with reference to the meridian and horizon, at any time during the last thirty 
years of the nineteenth century. The discussion of eclipses, and the elucidation of the means whereby we can 
calculate the absolute distances and bulks, and comparative weights of some of the heavenly bodies, are within 
the range of the simpler mathematics ; the only points involved, not included in the ordinary arithmetic, being 
the ratio of areas to squares, and contents to cubes, of like dimensions of similar figures, the composition of 
momenta, the analogies of plane and spherical right-angled triangles, and the addition of logarithms to find the 
product of their corresponding numbers. The elements of distance and bulk have been recalculated to the latest 
determinations of the solar parallax. 

The text is susceptible of verbal amplification, at the discretion of the teacher. The foot-notes are intended 
to serve, at once, as a table of contents, and as the groundwork of questions on the text. When they are used 
interrogatively, the pupil should be required to give a full explanation or definition of the subject referred to 
in each note. It is recommended that the student transfer the principal star groups to slate or paper, without 
outlines or letters. ...... 



CONTENTS. 



Earth's Motion ; on her own axis, and around the Sun ; Phenomena ; Circles of the Sphere ; Angular Meas- 
ures. 5-9 

Fixed Stars. Distances and Names ; Sun's Annual Journey along the Ecliptic ; Table. - 10-12 

Map No. I. Stars near the North Pole ; the Dipper ; Chair ; Ursa Minor ; Cepheus ; Draco. - - 13-16 
Map No. II. Stars near the Vernal Equinox ; Square of Pegasus ; Perseus ; Andromeda ; Lacerta ; Pisces ; 

Aries ; Musca ; Trianguli. - - ........ 17-19 

Map No. III. The Zodiac ; Cetus ; Phoenix ; Eridanus. ........ 20-21 

Map No. rV. Three to six hours in Right Ascension; Perseus; Taurus; The Pleiades; Auriga; Orion; 

Hydrus; Reticulum Rhomboidalis ; Doradus. --------- 22-24 

Map No. V. Gemini ; Telescopium Herschelium ; Cancer ; Canis Minor ; Canis Major ; Lepus ; Columba 

Noachi ; Lynx ; Camelopardalus. .....-..-. 25-27 

Map No. VI. Ursa Major ; Canes Venatici ; Leo ; Leo Minor. ....... 28-29 

Map No. VII. Virgo ; Coma Berenices ; Crater ; Corvus ; Hydra. ------ 30-31 

Map No. VIII. Libra ; Scorpio ; Ara ; Triangulum Australis ; Ophiucus et Serpens ; Norma Euclidis ; Circinus. 32-34 
Map No. IX. Taurus Poniatowski ; Aquila et Antinous ; Delphinus ; Sagittarius ; Corona Australis ; Micro- 

scopium ; Grus ; Indus et Pavo ; Telescopium. ........ 35-36 

Map No. X. Capricornus ; Aquarius; Piscis Australis; Pegasus ; Equuleus. ..... 37-38 

Map No. XI. Bootes ; Corona Borealis ; Hercules ; Lyra. ....... 39-40 

Map No. XII. Argo ; Robur Caroli ; Stars near the South Pole ; the Milky Way. - - - 41-42 

Map No. Xni. Cygnus ; Centaurus et Crux ; Lupus. -------- 43-44 

Table of Fixed Stars. Magnitudes ; Names ; Right Ascensions, North Polar Distances, Longitudes, and 

Latitudes on January 1st, 1875 ; Annual Variations. -...--■ 45-53 
Culminating, Rising and Setting. Ascensional Ditlerences; Refraction; To Find Right Ascension and Decli- 
nation from Longitude and Latitude. --------- 54-59 

Map No. XIV. Principal Stars Visible in North Latitude 40° ; Positions with reference to the Meridian and 

Horizon. - 60-61 

The Solar System. Jupiter, Venus, Mercury, Mars, Saturn, Uranus, Neptune ; Phenomena of Motion ; 

Heliocentric and Geocentric Positions ; Tables of Places from 1870 to 1900. ... - 62-70 

The Moon. Lunation ; Parallax ; Eclipses ; Measures of Time ; Chronology. ----- 71-78 
Distance and Bulk. Measuring the Earth and Moon ; Sun's Parallax ; Earth's Orbit ; The Sun ; Laws of 

Motion ; Mutual Attraction and its Results ; Precession ; The Tides. - 79-88 

Elements of the Solar System. Distances, Magnitudes, Bulks, etc., of the Planets and Luminaries. - 89-90 

Other Members of thf Family. Planetoids; Rings; Satellites, Comets; Aerolites. - - - 91-95 

The Fixed Stars. Parallax; Distances; Numbers; Magnitudes ; Light; Individual Motion ; Common Origin. 96-98 

Absolute Motion of the Solar System. Sun's Orbit ; Real Paths of the Earth and Moon. - - 99-100 

Index. - - - - 101-104 



INTRODUCTORY. 



1. The study of Astronomy includes two classes 
of objects — the stationary, and the wandering. 

2. The first class consists of the Fixed Stars ; so 
called, not because they are absolutely immovable, 
but for the reason that they change their relative 
positions very slowly, a thousand years making but 
little difference in their apparent locations with 
regard to each other. 

3. The second class comprises the Sun, Moon, 
Planetary Bodies, Asteroids, Comets, etc. ; they 
change their apparent places among the fixed 
stars with varying degrees of rapidity. Their 
paths in the heavens can only be traced out by 
one who has an ocular acquaintance with the lead- 
ing members of the first named class. 

4. The fixed stars appear to be set in the surface 
of a hollow sphere. If we watch them attentively 
for an hour or two, ou a bright night, we notice a 
connected movement. Those in the Eastern part 
of the heavens are slowly rising, those in the South 
are passing towards the West, and those in the 
"West are sinking towards the horizon. If, stand- 
ing any where in the Northern States, we face the 
North, and look up about half-way between the 
point overhead and the horizon, we may select any 
star, and, following its movements, see that it trav- 
els around but a small circle ; and there is one dull 
red star, shining out timidly in the midst of com- 
parative blankness, whose circle of apparent travel 
is so small, that the aid of an instrument is neces- 
sary to enable us to detect a movement. This is 
called the Pole Stag. 

5. This apparent movement of the stars is caused 
by the motion of the earth on its axis. The earth 



is a large globe, nearly eight thousand miles in 
diameter (the greatest distance through it is 
41,847,200 feet). We live on its exterior, the 
upright position at any place being perpendicular 
to the surface at that spot ; the centre of the globe 
is, every where, the point to which all bodies tend 
to fall, in obedience to the law of attraction of 
gravitation. The earth turns round once in twenty- 
four hours, in just the same way that a school 
globe is rotated on its axis ; except that the earth 
moves in space, with no frame work to support it. 

(?. Take a round ball, of yarn (or an orange), and 
run a piece of wire through its centre, making it 
pass entirely through the ball. Hold one end of 
the wire firmly in the hand, pointing the other end 
in the direction of the North, but sloping upwards, 
about midway between the level and upright posi- 
tions ; turn the ball slowly round on the wire. If 
a small insect were gummed fast to the surface of 
the ball, at a little distance from the northern end 
of the wire, he would preserve his position with 
regard to the centre of the ball, but, at each rota- 
tion, every visible object would appear to move 
round in a circle, the centre of which would be in 
the wire. 

7. Enlarge the ball to a globe of nearly eight 
thousand miles in diameter, replace the insect by 
a human being, held to the surface by the attrac- 
tion of gravitation, let the globe rotate in space, 
instead of being sustained on a wire, and let the 
stars be the surrounding objects; we have the 
earth in motion. The two points on the surface, 
corresponding to those cut by the wire, are called 
The Poles. . A line passing from one pole to the 



ASTRONOMY. 



other would be the earth's axis ; a circle traced 
around the surface, equally distant from the two 
poles, and marking off the globe into two halves, 
each of which would have one pole in the centre 
of its curved surface, would coincide with the equa- 
tor. A circle passing around the globe, through 
both poles, and dividing the equator into two 
equal semi-circles, would be a circle of the meri- 
dian. 

8. A circle of the meridian passing through any 
point on the earth's surface, is the meridian of that 
place ; and Avhen a straight line, joining the cen- 
tres of the earth and a star, would cut this circle 
at any point in its circumference, the star is said 
to be on the meridian of that place. 

19. If the line of the earth's axis were extended 
to the fixed stars, it would mark two opposite 
points which never change their position ; these 
are the Celestial Poles. The one adjacent to the 
pole star (Sec. 4) is called the North Pole ; the 
point opposite to it is the South Pole. Similarly, 
a line joining any two points in the Equator (Sec. 
7), if extended to the stars, would mark out among 
them, in the course of one rotation, a circle called 
the Equinoctial — everywhere equally distant from 
each of the celestial poles. A " circle passing 
through both poles would divide the Equinoctial 
into two equal semi-circles ; it would be a circle 
of the meridian. 

10. The expressions "would be," and "were," are 
employed in the above descriptions, for the reason 
that the polar points and the circles mentioned, 
are not actually marked, either on the earth or in 
the heavens; in both cases, the points through 
which the lines referred to would pass, are deter- 
mined by measuring from the fixed stars. Thus, 
we find the place of the North Pole by accounting 
it to be at a certain distance, in a certain direction, 
from the Pole Star. 

11. There is a second general movement observ- 



able among the stars. If we watch a group situ- 
ated near the Equinoctial, noting its position by 
sighting it along a wall at, say, 9 o'clock this even- 
ing, a week hence we shall find it arriving at the 
same apparent place, at a little after half past 
eight o'clock ; and a month hence it will be about 
7 o'clock instead of 9. Six months hence, the 
stars now overhead at 9 o'clock in the evening, 
will be overhead at 9 o'clock in the morning ; and 
not till next year, at this time, will the same jjlace 
be occupied at 9 o'clock in the evening, as now. 
The fixed stars gain nearly four minutes (3 min. 
56 sec.) daily, or two hours per month, or twenty- 
four hours in a year. On what do they gain ? 

12. On the Sun ; our time reckoning is meas- 
ured by his apparent motion in the heavens. The 
earth, while performing a daily rotation on her own 
axis, makes, each year, a revolution around the 
Sun. If we could stand on the solar surface, and 
view the earth, we should see her slowly moving 
forward, apparently among the fixed stars, making 
an entire circuit of the firmament in a little more 
than 365 days (365 d. 5 h. 48 m. 49 sec). To us, 
standing on the earth, it is the Sun that appears to 
make the journey. When he is on the meridian' 
(Sec. 8), we say it is noon, and the time between 
any two consecutive appearances of the Sun on the 
meridian is one day, which we artificially divide 
into twenty-four hours. But in that interval of 
time, the Sun has apparently passed over nearly 
one part in 365 of his annual journey, changing his 
place among the fixed stars by that amount, and a 
star near his apparent path will arrive on the meri- 
dian, on the second day, as much sooner as is 
given by the following proportion : 

As the time of the annual circuit is to one day, 
so is the time of one diurnal rotation to the time 
gained by a star; or, 

As 365 d. 6 h. is to 1 day, so is 24 hours to 3 
min. 56 sec, nearly. 



THE EARTH'S IOTIOI 



13. The Sun's pathway among the stars is called 
the Ecliptic. This circle does not coincide with 
the Equinoctial, but makes an angle with it of a 
little more than one quarter of a right angle. We 
may illustrate the relations of the two circles by 
recurring to the ball and wire (Sec. 6). Let a 
lamp, placed nearly in the centre of a large round 
table, represent the Sun, and the circumference of 
the table the path of the earth. Hold the wire 
pointing northward, as before, but let it slope less 
from the perpendicular — leaning only about one 
fourth of the angle towards the horizon. Then 
move the hand slowly around the edge of the table, 
always keeping the wire at the same inclination 
towards the North, and turning the ball round on 
the ware at the same time. The slope of the wire, 
as referred to the flat surface of the table, will rep- 
resent the position of the earth's axis with regard 
to a plane surface passing through every point in 
the Ecliptic circle. 

11. The Ecliptic and Equinoctial intersect each 
other in two opposite points, which are passed 
over by the Sun, respectively, about the 20th of 
March and the 23rd of September in each year. 
These are called the Equinoxes, because when the 
Sun is passing those points, the days are about 
equal in length to the nights, all over the globe. 

15. The following diagram shows the position 
of the earth's axis with regard to the plane of the 
Ecliptic : The central figure represents the globe, 
with the North Pole (at A) pointing in an oblique 
position. The curve BCD represents one half of 
the equator ; the globe rotates in the direction B 
to C, C to D, the journey from B to C being made 
in about six hours, that from C to D in six hours, 
and the entire rotation, from B to B again, in a 
little less than twenty-four hours. The surround- 
ing circle represents the Ecliptic, the page on 
which it is printed corresponds to the plane of the 
Ecliptic, and passes through the centre of the 




globe, cutting the Equator in the points B and D. 
If the earth simply rotated on her own axis, then, 
to a spectator at E, it would be noon when the Sun 
was at S, the luminary then being in a right line 
with the earth's centre, and F, which is a point in 
the meridian F E A I C G ; six hours afterwards 
the rotation of the earth would carry that meridian 
round to the position of the curved line BAD, 
and the Sun would then be near the western hori- 
zon ; six hours still later, the meridian would be 
carried half way round, and the spectator would be 
at I, it being then midnight ; in twelve hours 
more the earth -would have completed an entire 
rotation, bringing the spectator again to @, with 
the Sun at S on the meridian. 

16. But owing to the annual revolution, it will 
still lack nearly four minutes of noon, because dur- 
ing the time of one rotation on her axis, the earth's 
motion around the Sun will have caused him to 
appear to have moved forward in the Ecliptic to 
T. A fixed star at S would return to the meridian 



ASTRONOMY. 



at equal intervals of 23 h. 56 m. 4 sec, and make 
366^ revolutions, while the Sun made 365^ appa- 
rent daily circuits, just as the minute hand of a 
clock passes round the dial thirteen times in pass- 
ing the hour hand twelve times. The intervals 
between the successive returns of the Sun to the 
meridian of any place average twenty-four hours ; 
but these intervals are not all exactly equal. The 
Sun is not in the exact centre of the earth's orbit, 
and as she moves more rapidly when on that side 
of her orbit nearest to him, than when at her far- 
thest distance, the Sun's apparent daily motions in 
the Ecliptic are unequal, and that body is some- 
times on the meridian a little before, and at other 
parts of the year a little after, the time indicated as 
noon by a clock which measures equal days of 24 
hours each. This difference is called the Equation 
of time, and its direction is indicated by the expres- 
sions " Clock fast," or " Clock slow." The differ- 
ence between Mean (clock) noon, and Solar (Sun) 
noon, is given in most almanacs, for each day of 
the year. 

17. The sun is seen in the position S, about the 
21st of June ; the North Pole, A, is then turned 
partially towards him, and to a spectator at any 
part of the surface between the pole and the equa- 
tor, B C D, he is longer above the horizon than 
below. It is midsummer ; the stars at W are seen 
on the meridian at midnight. Three months after- 
wards — September 23rd — the Sun will have pro- 
gressed to the position V ; he is then on the Equi- 
noctial, in the plane of the Equator, BCD, and 
the days and nights are of equal length. The stars 
at Z are now seen on the meridian at midnight. 
In three months more — December 22nd — the 
Sun is seen at W ; the north pole is then partially 
turned away from him, and the nights in the north- 
ern hemisphere are longer than the days ; it is 
midwinter, but those living on that half of the 
earth's surface which is nearest to the south pole, 



have the long days and the short nights, with the 
warm weather of the summer season. The stars 
at S, which were obscured by the Sun's presence 
in June, are now visible on the meridian at mid- 
night. Still another three months brings the Sun 
to Z — March 20th — where he is again on the 
Equinoctial, and the days and nights are once 
more equal. This is the Vernal, or Spring Equi- 
nox. 

18. The two great circles, the Ecliptic and 
Equinoctial, thus intersect each other at the points 
Z and V. Astronomers have agreed to take the 
first — the Vernal Equinox — as the one from which 
the distances of the heavenly bodies shall be meas- 
ured, and to which they shall be referred for com- 
parison of their mutual positions. The measure- 
ments are made on both circles, proceeding in the 
direction Z S V W Z, and sideways from them 
towards the poles. 

10. The distance from the Vernal Equinox, 
measured on the Equinoctial, is called Right Ascen- 
sion. 

20. The distance sideways from the Equinoctial 
is called Declination, and is called " North," or 
" South," according as it is measured towards the 
North or South Pole. Sometimes (see Sec. 136), 
instead of the Declination, it is preferred to use the 
distance from the North Pole (abbreviated to 
" Nor. Pol. Dis."). Both are measured on a circle 
of the meridian passing through the apparent cen- 
tre of the star. 

21. Distance from the Vernal Equinox, meas- 
ured on the Ecliptic, is called Longitude. The 
distance sideways from the Ecliptic is called Lati- 
tude, and is North or South as in the case of Decli- 
nation. 

22. These dimensions are not taken in feet and 
inches, or miles. We do not attempt, in this con- 
nection, to measure actual distances, but to find 
the magnitude of the angle formed by straight 



ANGULAR M EAST RES. 



lines, from stars or points, meeting at the eye of 
the observer. For this purpose the circle is sup- 
posed to be divided into 360 equal parts, called 
Degrees, and each of these degrees into 60 equal 
parts called Minutes, and each minute into 60 equal 
seconds. A quarter of the circumference of the 
circle, or 90 degrees, is the measure of a right 
angle. The angle included between the planes of 
the Ecliptic and Equinoctial is 23 degrees, 27 min- 
utes, and 20 seconds ; thus expressed: 23° 27' 20". 
23. The Ecliptic is further divided into twelve 
equal parts, called Signs, each containing 30°. 
The following are their names in Latin, with the 
characters used to represent them. The signs are 
shown in their order, around the preceding dia- 
gram (Sec. 15), the character being placed at the 
beginning of the space denoted by it : 



°P Aries. SI Leo. 

tf Taurus. TiJJ Virgo. 

n Gemini. =c= Libra. 

S3 Cancer. TU Scorpio. 



4 Sagittarius. 

Y3 Capricornus. 

£? Aquarius. 

}£ Pisces. 



24. These signs must not be confounded with 
twelve star groups, bearing the same names, to be 
mentioned subsequently. The spaces were thus 
named by the early astronomers, many years 
before the Christian Era, to signify the character 
of the season experienced while the Sun was appa- 
rently passing through them ; and the stars then 
within those limits were called by the same names. 



But since that time the stars have all gradually 
moved forward, so that those then in °p are now in 
b , those then in 8 are now in n, etc. Both Signs 
and star groups have retained the names then 
given, the group called " Aries " being now in the 
space called " Taurus." The Longitude of a star is 
often counted on the Ecliptic from 0° to 360°, but 
generally reckoned as so many degrees in a certain 
sign. Thus the Longitude 168° 3' 9" is expressed 
as TTg. 18° 3' 9"; that is, 150° for five whole signs, 
and the overplus counted as from the beginning of 
TTQ, the sixth sign. 

25. This third connected movement of the stars 
is much slower than either of the two already 
spoken of (Sees. 4 and 11). One revolution occu- 
pies many centuries, and the movement requires 
many years of patient watching to measui-e it ; the 
amount of change is 50^ seconds annually, or 1° in 
about 72 years. It results from the fact that the 
earth's axis, which we have hitherto considered as 
always pointing to the same j)art of the heavens, 
has a slow, swinging motion, describing a circle in 
the heavens, of a diameter equal to twice the angle 
formed by the Ecliptic and Equinoctial, in about 
25,750 years. This causes the points of intersec- 
tion of these two circles to recede along the Eclip- 
tic, making one round in that time, and causing 
the stars to appear to move forward with respect 
to the Equinoctial points, from which their Longi- 
tudes and Right Ascensions are measured. This 
motion is called the Precession of the Equinoxes. 



Define and explain (the figmes refer to the sections) : 

2. Fixed stars. 3. Moving bodies. 4. Diurnal motion ; Pole star. 5. Earth's diameter, time of rotation ; centre of 
gravitation. 6. Earth's motion in miniature. 7. Motion in space ; axis ; equator ; circle of meridian. 8. Meridian of 
any place. 9. Celestial poles ; equinoctial. 10. Imaginary lines. 11. Annual revolution ; daily progress of stars. 
12. Measure of time ; year ; earth journey ; noon ; divisions of day. 13. Ecliptic, angle with equinoctial ; illustration 
of annual motion. 14. Equinoxes. 15. Simple rotation. 16. Compound and unequal motion ; equation of time. 
17. Position of Sun each three months; summer and winter. 18. Intersections of ecliptic and equinoctial; origin of 
measures. 19. Eight Ascension. 20. Declination. 21. Longitude ; latitude. 22. Angular measure, degrees in circle ; 
subdivisions. 23. Signs ; characters and names. 24. A necessary distinction ; two modes of expressing longitude. 
25. Precession of equinoxes ; rate , effect. 



10 



ASTKONOMY. 



26. Distances in Right Ascension are also reck- 
oned in degrees and minutes, but it is generally 
more convenient to count them in time, the Right 
Ascension of a star being equal to the number of 
hours and minutes which elapse between the Meri- 
dian passage of the Vernal Equinox and that of 
the star. The clock used must, however, be one 
showing sidereal time ; that is, marking the lapse 
of 24 hours in the same time that the ordinary 
clock notes 23 h. 56 m. 4 s., or between the two 
consecutive times of a fixed star passing the Meri- 
dian (Sec. 12). Twenty-four hours thus measures 
the passage of 360° ; one hour, therefore, is equiv- 
alent to 15°, and 1° is equal in value to four min- 
utes of time. The minutes and seconds of time 
are marked " m," and " s," to distinguish them 
from minutes and seconds of space (Sec. 22). 

27. The Ecliptic is not only the line of the 
Earth's annual revolution, but it is also remarkable 
as being the middle of a narrow band, or zone, of 
about 16° in breadth, within which all the princi- 
pal members of the solar system, and many of the 
smaller ones, are always found when seen from 
any point on the Earth's surface. It is hence 
important to be able to trace out its course among 
the fixed stars, the planets Jupiter and Saturn 
being always close to the Ecliptic, and the Moon, 
Venus, and Mars, never more than about 8° dis- 
tant. For this reason most of the following maps 
are projected with the Ecliptic as the principal line, 
and a straight one ; the Equinoctial, when within 
the "limits of the map, running obliquely. The 
maps are constructed on a scale of 10°, on the 
Ecliptic, to the inch. 

28. The fixed stars are scattered irregularly 
over the heavens, in uncounted numbers ; those 
ordinarily visible to the naked eye are not numer- 
ous. The most prominent are mapped out in 
this book, with the position of an irregular band 
of minute stars and star clouds, running around 



the heavens, and called the Galaxy, or Milky 
Way. 

29. The early observers of the stars divided 
them into groups, often fanciful, but still useful ; 
those groupings are recognized, with but few 
changes, by astronomers of the present day. The 
shapes chosen were generally those of natural and 
common objects. "We may not be able to discern 
lions, bears, goats, fishes, dogs, or men, among the 
stars, but for that we are not responsible ; it is a 
very convenient arrangement, and one not yet 
improved upon. 

30. Each of these groups is called a Constel- 
lation. The stars comprised in each are of vari- 
ous degrees of brightness — the greater prominence 
being probably due in some instances to relative 
nearness, in others to greater actual size. The 
largest in appearance are said to be of the first 
magnitude, those next in brightness are classed as 
of the second; those so faint as to be but just dis- 
cernible with the naked eye under the most favor- 
able circumstances, are enumerated as of the sixth 
magnitude; stars seen only by the aid of a teles- 
cope, are cl'assed from the seventh to the sixteenth 
magnitudes, inclusive ; and clusters of telescopic 
stars, or of matter which the telescope has not yet 
resolved into stars, are called Nebulae. On the 
following maps are shown the relative positions of 
all stars from the first to the fifth magnitudes inclu- 
sive, within about 25° of the Ecliptic, and all stars 
of greater magnitude than the fifth, outside of those 
limits, with a few smaller ones in special cases, and 
a few of the more remarkable nebulae. The appa- 
rent relative sizes are distinguished as follows : 

Stars of the first magnitude, with eight rays. 
Second mag., seven rays. Third mag., six rays. 
Fourth mag., five rays. Fifth mag., four rays. 
Nebulous clusters, by a circle, enclosing a dot. 



DISTANCES AND NAMES. 



11 



31. The Stars are individualized by giving 
proper names to the most prominent, and also by 
naming all with the letters of the Greek alphabet, 
usually giving the first letter to the largest star in 
the constellation, the next letter to the second star 
in apparent magnitude, and so to Omega, after 
■which the Roman letters, and sometimes Arabic 
numerals, are employed. The name of the con- 
stellation is put in the genitive case. Thus the 
largest star in the constellation, Leo — the Lion — 
is called " Regulus," and enumerated as a (Alpha) 
Leonis. The following is the Greek alphabet. 

a Alpha. i Iota. p Rho. 

• j3 Beta. x Kappa. <r Sigma. 

y Gamma. -i Lambda. r Tau. 

d Delta. p. Mu. u Upsilon. 

e Epsilon. v Nu. <p Phi. 

C Zeta. f Xi. x Chi. 

i) Eta. o Omicron. ip Psi. 

Theta. n Pi. w Omega. 

In a few cases one letter is applied to two or 
more stars in the same constellation, and followed 
by a small numeral; as a 1 , and a". The stars so 
marked belong to a subordinate group, generally 
with an independent motion of its own, its mem- 
bers revolving around a common centre. 

32. The point in the heavens directly overhead 
is called the Zenith. The direction "Northward," 
in the heavens, is always towards the North Pole, 
not to the northern point of the horizon. " East- 
ward" is always in the direction of increased Right 
Ascension, as from 11 hours towards 12 hours, and 
" Westward" is in the direction of decreased Right 
Ascension ; the latter fact should be especially 
borne in mind in the case of stars between the 
Pole and the horizon, as then the direction is 
exactly the reverse of that understood by the use 
of the same words in reference to points on the 
Earth's surface. 



33. The following table shows the Sun's Longi- 
tude, both as counted direct from the Vernal Equi- 
nox, and as reckoned by signs, with his Right 
Ascension in time, and the Equation of time, for 
the noon of the 1st and 15th days of the twelve 
months next preceding February 29th in Leap 
Year. The Longitude and Right Ascension for 
intermediate days may e-isily be found by propor- 
tion. The table is nearly correct for any year in 
the last half of the present century, and the Sun's 
place may be found very nearly by adding 45' to 
the Longitude, and 3 min. to the Right Ascension, 
for any day in the first twelve months after Leap 
Year's day ; 30' and 2 min. for the second twelve 
months ; and 15' for Longitude, and 1 min. for 
Right Ascension, for the third twelve months after 
February 29th, to the quantities given in the table. 

34. The Right Ascension of the Sun on any 
day is equal to the time that the Sun passes the 
Meridian before the Vernal Equinox (Sec. 26). 
The Equation of Time (Sec. 16) is the difference 
between the clock and the Sun If, therefore, we 
apply the Equation as given in the last column of 
the table, adding it to, or subtracting it from, the 
Sun's Right Ascension, as the sign is -f- (plus), or 
— (minus), we shall know the number of hours 
and minutes that the Vernal Equinox passes the 
meridian, above the Earth, before Clock, or Mean, 
Noon. This corrected Right Ascension is called 
Sidereal Time. For all ordinary purposes of obser- 
vation the Equation of time may be neglected. 

35. From the Right Ascension of a Fixed Star 
(adding 24 hours, if necessary) subtract the Side- 
real Time for the day required ; the remainder is 
the time past noon when the Star will be on the 
Meridian above the Earth. To the Sidereal time 
(or the Sun's Right Ascension if accuracy be not 
required) add the time past noon ; the sum will 
give the Right Ascension on the Meridian at that 
time. 



12 



ASTKONOMY. 



March 1 - 
" 15 

April 1 
" 15 - 

May 1 
" 15 - 

June 1 

" 15 - 

July 1 
" 15 - 

August 1 - 
" 15 

September 1 
" 15 

October 1 - 
" 15 

November 1 
" 15 

December 1 
" 15 

January 1 - 
" 15 

February 1 
" 15 
" 29 





Sun 


s Longitude. 




Right Ascension. 


Equation of Tia 


340° 


47' 


= 


X 


10° 


47' 


22h. 


49m. 


5 s. 


_ 


12m. 


36s. 


355° 


47' 


= 


K 


25° 


47' 


23h. 


44m. 


31s. 


— 


8m. 


48s. 


11° 


37' 


= 


op 


11° 


37' 


Oil. 


42m. 


41s. 


_ 


4m. 


15s. 


25° 


21' 


= 


T 


25° 


21' 


lh. 


34m. 


Is. 


— 


0m. 


is. 


40° 


55' 


- 


8 


10° 


55' 


2h. 


33m. 


56s. 


+ 


2m. 


59s. 


54° 


27' 


= 


8 


24° 


27' 


3h. 


28m. 


20s. 


+ 


3m. 


51s. 


70° 


46' 


= 


n 


10° 


46' 


4h. 


36m. 


33s. 


+ 


2m. 


30s. 


84° 


10' 


= 


n 


24° 


10' 


5b. 


34m. 


34s. 


— 


0m. 


7 s. 


99° 


25' 


= 


S3 


9° 


25' 


6h. 


40m. 


59s. 


_ 


3m. 


27s. 


112° 


46' 


= 


£3 


22° 


46' 


7h. 


38m. 


20s. 


— 


5m. 


36s. 


12 9 C 


1 


= 


Si 


9° 


1' 


8h. 


45m. 


49s. 


_ 


6m. 


2s. 


142° 


27' 


= 


a 


22° 


27' 


9h. 


39 m. 


14s. 


— 


4m. 


14s. 


158° 


51' 


= 


m 


8° 


51' 


10b. 


41m. 


51s. 


+ 


Om. 


9s. 


172° 


28' 


= 


m 


22° 


28' 


llh. 


32m. 


20s. 


+ 


4m. 


53s. 


188° 


9' 


= 


^ 


8° 


9' 


12b. 


29m. 


56s. 


+ 


10m. 


21s. 


201° 


59' 


= 


^ 


21° 


59' 


13b. 


21m. 


16s. 


+ 


14m. 


10s. 


218° 


56' 


- 


m 


8° 


56' 


14b. 


26m. 


10s. 


+ 


16m. 


18s 


233° 


1' 


= 


m 


23° 


1' 


15b. 


22m. 


27s. 


+ 


15m. 


12s 


249° 


12' 


= 


* 


9° 


12' 


16h. 


30m. 


is. 


+ 


10m. 


43s. 


263° 


25' 


= 


# 


23° 


25' 


17b. 


31m. 


18s. 


+ 


4m. 


34s. 


280° 


45' 


= 


V3 


10° 


45' 


18h. 


46m. 


46s. 


_ 


3m. 


48s 


295° 


1' 


= 


V3 


25° 


1' 


19b. 


47m. 


51s. 


— 


9m. 


41s 


312° 


18' 


- 


JSf 


12° 


18' 


20h. 


59m. 


4s. 


_ 


13m. 


58s 


326° 


28' 


= 


/8? 


26° 


28' 


21h. 


54m. 


49s. 


— 


14m. 


24s 


340° 


33' 


= 


X 


10° 


33' 


22h. 


48m. 


13s. 


— 


12m. 


37s 



Define and explain (the figures refer to the sections) : 

26. Right Ascension in time. 27. The Zodiac ; its width and medial line ; what it includes ; projection of maps. 
28. Distribution of fixed stars. 29. Constellations. 30. Classification of magnitudes. 31. Naming the stars ; Greek 
alphabet ; other marks. 32. Zenith ; East and West in the heavens. 33. Sun's Longitude and Right Ascension through 
the year ; equation of time. 34. Clock noon ; Sidereal time. 35. When a star is on the meridian. 



MAP NO. I. 



36. We commence the work of tracing out the 
relative locations of the fixed stars, with the group 
called The Dipper — the most prominent part of 
a constellation known as Ursa Major. It is a well 
known and easily recognized assemblage of stars ; 
is always above the horizon of the Northern, and 
of the northern tier of the Southern, States ; lies 
directly across the Equinoctial Colure (a meridian 
circle passing through the Equinoxes, hence some- 
times called the first celestial meridian), and forms 
an easy guide to the position of the Pole Star. The 
Dipper is shown in the lower right hand corner of 
the map. It is visible in this position, on moder- 
ately clear nights, at the time the Vernal Equinox 
coincides with the meridian above the earth, as 
shown in the preceding table. Thus, on December 
1st, the Sidereal time is 16 h. 30 m. + lOfm. = 
16h. 40f m. ; and at that time before noon, or at 
'I h. 19^ m. in the evening, the Dipper occupies the 
position shown on the map ; it is visible in nearly 
the same position for an hour before and after that 
time. 

37. From this position the Dipper slowly rises 
towards the right, in an oblique direction, and six 
hours afterwards is in the North-eastern part of 
the heavens, and. 30° to 40° above the horizon, with 
the handle pointing downward. Turn the map so 
that the Dipper will be in the upper right hand 
corner, and it will show the appearance then ; for 
example, at 1 h. 19 m. in the morning of December 
2nd. From this position the group still rises, till 
six hours later — as at 7 h. 19 m. in the morning 
of December 2nd — it is on the meridian, a few 
degrees north of the Zenith, with the handle 
towards the right ; as shown by turning the map 



upside down, bringing the Dipper to the upper left 
hand corner. Six hours still later the Dipper occu- 
pies the position shown by turning the map so as 
to bring the group into the lower left hand corner, 
the handle pointing upwards, in the North-western 
quarter of the heavens. The cause of these changes, 
both in position and time, has been explained in 
Sections 5 and 12. 

38. The seven prominent stars in the Dipper 
are lettered from a to y inclusive (Sec. 31), begin- 
ning at the top of the side furthest from the handle 
— the Western side (Refer to Sec. 32) Each has 
also a proper name. They are : a, Dubhe ; /?, 
Merak; y, Phecda ; 3, Megrez ; e, Alioth ; C, 
Mizar; rj, Alkaid, called also Benetnasch. Dubhe 
and Merak are known as the Pointers, because, 
in whatever part of its daily circuit the Dipper may 
be, they always point towards the North Pole. On 
the map this point is at the intersection of the two 
right lines, near the middle of the right hand 
margin. Near it is a dull red star of the 2nd mag- 
nitude (Sec. 30) marked a, and named Alruccabah. 
(Sec. 4). It is so near the Pole that its place is 
often accepted as that of the Pole itself. It is 27° 
34£' from Dubhe, and a little outside of a line from 
Merak through Dubhe. The distance may be 
gauged very nearly by remembering that it is about 
one tenth greater than that between Dubhe and 
Alkaid in the extremity of the handle. The dis- 
tance from Dubhe to Alkaid is 25° of a great cir- 
cle ; from a to S is 10°, these two forming the top 
of the basin. It will be found very convenient to 
transport these dimensions in the mind's eye, as 
measuring rods of angular values in other portions 
of the heavens. 



14 



ASTEONOMY. 



39. On the other side of the Pole Star, about 
equally distant from it, and lying also on the Equi- 
noctial colure, is another notable group, commonly 
called The Chair. It is represented in the upper 
right hand corner of the map, and is the principal 
portion of the constellation Cassiopeia. Its circle 
of apparent revolution about the pole is of the same 
magnitude as that of the dipper, and it is alter- 
nately near the zenith, or near the horizon, twelve 
hours after that group has occupied the same posi- 
tion. The center of the Chair passes the meridian 
a few minutes after the Vernal Equinox (Sec. 34). 

40. The Chair and the Dipper are always avail- 
able to the observer in the northern hemisphere, 
and both are always above the horizon of the north- 
ern States. They furnish us with the elements of 
a very important surveying line — that from which 
the Right Ascensions of all the stars are measured. 
The perpendicular line on the map represents the 
northern portion of the Equinoctial colure (Sec. 36) 
which cuts the Equinoctial at right angles, at the 
points of its intersection with the Ecliptic (Sec. 18). 
The star marked j3 — Chaph — in the back of the 
Chair, and Mugrez, are very nearly on this line, the 
Chair end of which runs through the Vernal, and 
the Dipper end through the Autumnal, Equinox. 
These two stars are nearly equidistant from the 
Pole, and, in addition, enable us to find its position 
with reference to the Pole Star, which the map 
shows to lie exactly on a line from d in the Chair 
to £ in the dipper. The following are their places 
for January 1st, 1875 : 



Star. Name. Rt. Ascension. Declination. 

13 Cassiopeia? Chaph Oh. 2m. 31s. 58°27'37" 

d Ursa? Maj. Megrez 12h. 9m. 14s. 57°43'36" 

a Ursa? Min. Alruccabah lh.12m.55s. 88°38'35" 

The Pole Star is therefore 1° 21' 25" from the 
Pole, towards the Chair, and makes an angle of 



lh. 12m. 55s, or 18° 13' 45" (Sec. 26) with the 
colure, inclining towards d Cassiopeia?. 

41. Cassiopeia — The Lady in her chair. All 
of this constellation, except the head, is shown on 
Map No. 1. Its greater portion lies east of the 
Equinoctial colure. It is situated about half way 
between the North Pole and the Equinoctial, and 
contains 55 stars visible under the most favorable 
circumstances, but those shown in the figure are all 
that the student will easily recognize. Schedir — • 
a — a pale, rose-tinted star of the 3rd magnitude, 
in the bosom; Chaph — j3 — a white star of the 
2nd magnitude, in the back of the Chair; and y, a 
white star of the 3rd magnitude, in the lap, form a 
i-ight angled triangle, whose sides are about 5° 
each. Opposite to a is x, of the 4th magnitude, 
and a star of the 5th magnitude, just north of x, 
completes the square ; 3, of the 3rd magnitude, in 
the knee, and e, of the 3rd magnitude, in the for- 
ward foot, 5° apart, complete the front outline of 
the figure ; £ forms the southern corner of a simi- 
lar square of stars, but smaller than those in the 
body. The head of Cassiopeia, containing £, of 
the 4th magnitude, and the body, are in the Milky 
Way, the course of which is shown on the map. 

42. Ursa Minor— The Lesser Bear. The Pole 
Star, Alruccabah, is situated at the extremity of 
the handle of another dipper-shaped group, rather 
smaller, and composed of smaller stars, than that 
in Ursa Major (Sec. 36). The two stars, /?, of the 
3rd magnitude, and £ of the 4th, forming the top 
of the dipper, lie nearly in a straight line between 
Alkaid and Chaph. The handle forms the tail of 
Ursa Minor, and the basin gives the position of the 
body; Kochab — /? — the nearest to the great dip- 
per, is in the shoulder, and with y, of the 3rd mag- 
nitude, in the breast, 3° south east of /?, forms the 
front end of the little dipper ; they are pointers to 
7], of the 3rd magnitude in Draco ; d, of the 3rd 
magnitude, is about 4° south of a, and between 



CIRCUMPOLAR STARS. 



15 



them are two contiguous stars of the 5th magni- 
tude. The constellation contains 24 discernible 
stars. 

43. Cephetjs — Mythologically the king of Ethi- 
opia, and husband of Cassiopeia, is represented on 
the globe, in regal state, with crown and sceptre. 
The constellation lies northeast of Cassiopeia, the 
feet near the pole, and contains 35 discernible stars, 
of which only six are prominent. A line from 
Schedir — a Cassiopeia — through Chaph, produced 
20° further to the northeast,) will nearly pass through 
two stars, 4° asunder, the nearest of which is Alder- 
amin — a — a white star of the 3rd magnitude, in 
the left shoulder of Cepheus ; 8° north of a is 
Alphirk — /? — a white star of the 3rd magnitude, 
and these two form, with d in the head, of the 4th 
magnitude, and another of the 4th in the right 
shoulder, a diamond square of stars, of about 8° 
on each side. Er Rai — y — a yellow star of the 
3rd magnitude, in the knee, lies nearer the pole, 
and nearly on the colure, at the vertex of a trian- 
gle with /3 and No. 1, and 11° distant from each. 
The position of the foot of Cepheus, very near the 
pole, is marked by four stars of the 5th magnitude, 
with one in the ancle nearer to /. The head lies 
in the milky way. 

4:4. Draco — The Dragon. This constellation 
contains 80 discernible stars. When Cassiopeia is 
on the meridian above the pole, and the Dipper 
near the horizon, as in the map, a wedge-shaped 
group of bright stars, the point downwards, is in 
the northwest, about 35° above the horizon. It is 
nearly the same distance from the pole as are those 
two groups, and on the 18 hour circle ; this circle, 
a portion of which is represented by a straight line 
on the map, is perpendicular to the Equinoctial 
colure, cutting the Ecliptic in the beginnings of ® 
and Y3 (Sec. 23), and the Equinoctial at 6 and 18 
hours, forming the Solstitial colure. This group is 
the head of Draco, and circles around the pole 6 



hours after the Dipper, and 6 hours before Cassio- 
peia, its Right Ascension being 18 hours. It may 
also be found by tracing a line from 8 Cassiopeia 
through § Cephei, and another from Phecda 
through Megrez ; it is nearly at the junction of 
these two lines, about 35° from the Pole. The two 
bright yellow stars of the 2nd magnitude, Etanin 
— y, and Alwaid — /?, with £ of the 3rd magni- 
tude, form nearly an equilateral triangle of 5° on 
each side, a line from y through ?, almost touch- 
ing the pole; El Rakis — p. — in the nose, is 5° 
west of /?, and forms another triangle with it and 
a small star lying between p and £ . The Solstitial 
Colure on which y, and f — Grumium — lie nearly, 
passes through the poles of the Ecliptic, as well as 
those of the Equinoctial. The north pole of the 
Ecliptic is shown on the map, about 9° north of 
Grumium, and 23^° from the Pole Star, being 90° 
distant from every part of the Ecliptic Circle, as 
the pole of the earth's rotation is every where dis- 
tant 90° from the Equinoctial. The word " Pole " 
always means " the pole of the earth's rotation," 
unless otherwise described as the Pole of the Eclip- 
tic, or of some other circle ; for every circle of the 
sphere has its own pole on the surface, as every 
circle on a plane has its own center. 

45. The figure of the Dragon is a very irregular 
one, but it is easily traced in the heavens. From 
the head it proceeds eastward, nearly to x Cygni, 
of the 4th magnitude, 12° from Etanin; then 
turning north, it winds round d of the 3rd magni- 
tude, 13° from x, and thence curves irregularly 
round the Pole to the West, inclosing Ursa Minor, 
and taking in a circling line of several bright stars, 
including a, x, and A, all of the 3rd magnitude, 
near the Dipper, and between it and the pole ; 
Thuban — a — a pale star near the head of Ursa 
Minor, and about half way between the pointers 
of that constellation and Mizar, the middle star in 
the handle of the Large Dipper, is remarkable as 



16 



ASTKONOMY. 



having been the Pole Star many ages ago, then 
occupying the place now held by Alruccabah, and 
being at one time nearer to the Pole than the pres- 
ent Pole Star now is. The Precession of the Equi- 
noxes (Sec. 25) causes the stars near the pole to 
change their angular positions in Right Ascension 
more rapidly than those in the Zodiac — Alrucca- 
bah now increasing its right ascension by nearly 
20| seconds of time yearly. The longitude is 
increased about 50^" annually, the same in every 
part of the heavens. The places of the fixed stars, 
as given in this book, are those occupied January 
1st, 1875, and are near enough to the actual places 
for observing purposes, for several years before and 
after that date. 

4G. The forward half of Draco now winds round 
the pole of the Ecliptic, and the latter half formerly 
included the pole star of the world. The shape 
was probably assigned to the stars it now embra- 
ces, by the first observers, long before the changes 
made in other portions of the heavens by the Greek 
mythologists, earlier, even, than the time of the 
Pharaohs — assigned there for the purpose of sym- 
bolizing the unity of the two systems of diurnal 
and annual motion, and furnishing an imperishable 
record of Astronomical research and patriarchal 
wisdom in the days when books and paper 
were unknown. The North Pole Star was then 
between the two Dippers, which were always over 



the polar regions. The ancient Chaldeans had. 
even less knowledge of the character of the earth's 
surface near the pole than we have, and called it 
the " Country of the Bears ;" " Under the Bears " 
became a well understood equivalent for " The 
Northern Lands." The idiom was adopted by 
other peoples, and has not yet been totally swal- 
lowed up in the stream of Time, though the Pre- 
cession of the Equinoxes has carried the Great 
Dipper outside of the original track. It is, how- 
ever, remarkable, that Thuban resigned his place 
to the principal star in one of the Bear groups, 
and Draco yet partially encloses both poles ; still 
silently telling the old truth, but in new and less 
direct form. 

47 » A line from the foot of Cassiopeia through 
3 Cephei, and extended about 20° beyond d, 
would nearly touch Deneb — a — a brilliant white 
star of the 1st magnitude in the constellation Cyg- 
nus, which crosses the meridian very near the 
Zenith of the Northern States. About 5° South, 
and a little West of Deneb, is y of the 3rd mag- 
nitude, the two forming the shortest side of a 
triangle, with d of the 3rd magnitude, nearer the 
head of Draco. The four stars lying South-east 
from Alkaid, in the lower left hand corner of the 
map, are in the Constellation Bootes: Nekkar — ,3 
— of the third magnitude, is 1 6° South-east from 
Alkaid, in the line of the Dipper handle. 



Define and explain (the figures refer to tlie sections) : 

36. The Dipper ; its place ; guide to Pole Star. 37 Changes in position. 38. Pointers ; Alruccabah ; measures of 
10° and 25°. 39. The Chair ; opposite what ? 40. Equinoctial Colure ; Chaph and Megrez ; Pole Star and Pole. 41. 
Cassiopeia ; The Square ; Schedir ; knee and foot ; Milky Way. 42. TJrsa Minor ; small Dipper ; Alkaid to Chaph ; 
shoulder ; pointers to Draco. 43 Cepheus ; position ; Alderamin ; diamond figure ; Er Rai ; the foot. 44. Draco ; 
the head; Solstitial Colure; Six hours after the Dipper; Equilateral triangle; Etanin; Grumium; Pole of Ecliptic; 
Poles of other circles. 45. Course of Draco ; Thuban ; former Pole Star ; precession, effect near the Poles ; places of 
stars in this book. 46. Origin of Draco ; the two Dippers ; early records, 47, Deaeb ; Nekkar. 



MAP NO. II. 



48. This map is connected with the first by the 
Constellation Cassiopeia, represented near the mid- 
dle of the upper margin of the map, in an inverted 
position; the feet towards the pole, with Chaph 
on the curved line, in the right half of the Map, 
representing the Equinoctial Colure, and crossing 
the Equinoctial Circle at its intersection with the 
Ecliptic, in the first part of °P (Aries) near the 
lower margin of the map. 

49. The line from Megrez, through the pole to 
Chaph, if continued 30° farther South, will pass 
nearly through a bright white star of the 1st mag- 
nitude — a — named Alpheratz, in the head of 
Andromeda ; the line continued 1-4° still further, 
will pass a little West of Algenib — y — a yellow 
colored star of the 2nd magnitude, in the wing of 
Pegasus ; 14^-° still further South the line crosses 
the Vernal Equinox, which is easily located by 
remembering that it is a very little farther South 
of Algenib than that star is South of Alpheratz. 

50. These two stars form the Eastern side of a 
large square, with Markab, a white star of the 
2nd magnitude, and Scheat, a deep yellow star, 
also marked a and /?, in the constellation Pegasus. 
The last named two are just "West of the circle of 
23 hours of Right Ascension, and 12f° apart. 
They are shown near the right margin of the map. , 
Alpheratz and Algenib are on the meridian, about 
midnight on the 23d of September (page 12); 10 
P.M., on October 23rd; 8 P.M., on November 22nd; 
and 6 P.M. on December 21st. They are always 
near the meridian at the same time that the Dipper 
is near the horizon, as in Map No. 1 ; Alpheratz 
being then 10° or 15° South of the Zenith, in the 



Northern States. Markab and Scheat Pegasi come 
to the meridian one hour earlier. The quadrangle 
is known as The Square of Pegasus, and its 
position in the heavens should be made familiar, as 
it is of great service in locating the Ecliptic and 
Equinoctial, which, in that part of the heavens, 
have few other notable stars near them. 

51. A line drawn diagonally fiom Markab to 
Alpheratz, and prolonged to the Northeast, will 
pass a row of bright stars noted on the Map as 
Mirach, Almaach, and Mirfak. The middle three 
of the five form nearly the medial line of Andro- 
meda,— a in the head, /?, a yellow star of the 
2nd magnitude in the girdle, and y, an orange 
colored star of the 3rd magnitude, in the right foot. 
The last of the series is a, in the breast of Per- 
seus ; the other four are remarkable as lying nearly 
on successive hour circles, their Right Ascensions 
being as follows: a Pegasi, 22h. 58m. 32s; a An- 
dromeda?, Oh. lm. 16s. ; /3 Andromeda?, lh. 2m. 44s. ; 
y Andromeda?, lh. 56m. 14s. The gradual narrow- 
ing of the spaces between the hour circles, as they 
approach the Pole, is shown on the map ; it les- 
sens the angular distance as measured on the 
great circle of the sphere, in proceeding North- 
ward. The following are the distances between 
these mile-stones in the firmament: Markab to 
Alpheratz 21°, Alpheratz to Mirach 14°, Mirach to 
Almaach 13°, Almaach to Mirfak 16°. 

52. A line from s, in the foot of Cassiopeia, 
South through Almaach, will pass Hamal 19° 
beyond, a yellow star of the 2nd magnitude — a 
— in the head of Aries. On the same line, 26-|° 
South from Hamal, lies Mira, in Cetus — a variable 



18 



ASTRONOMY. 



star, marked on the map as of the 2nd magnitude. 
The circle of 2 hours of Right Ascension, leaves e 
Cassiopeia? a little to the West, and passes through 
Hamal, passing, also, /? Trianguli, a star of the 4th 
magnitude, about half way between Almaach and 
Hamal, and runs a little East of El Rischa, a pale, 
greenish colored star of the 3rd magnitude, which 
is 7° Northwest from Mira, and nearly 21° South 
of Hamal. The three last named are important ; 
the Equinoctial passes nearly midway between El 
Rischa and Mira, and the Ecliptic nearly midway 
between El Rischa and Hamal. 

53. Mirfak — a Persei — (Sec 51), a brilliant 
lilac star of the 2nd magnitude, is 18° Southeast 
of s Cassiopeia?; .nearly midway between them is 
■q Persei, in the sword arm, and between a and -q is 
y of the 3rd magnitude, near the shoulder. This 
line is further prolonged to 8 of the 3rd magnitude, 
11° from 7). South of y 12°, and &\° Southwest 
from d, is Algol — /? Persei — a dull white star of 
the 2nd magnitude, and marking the location of 
the third hour circle. A line from Algol to d 
' makes a right angle with a line from <Ho y. North- 
east of 8 and ij, and forming with them a trapezium 
very narrow at the top, are two stars of the 4th 
magnitude, the principal ones in Camelopardus — 
a constellation not important enough to be repre- 
sented on these maps. The Milky Way runs 
Northwest through the upper part of Perseus, 
then turning West takes in the body of Cassiopeia, 
and, passing nearly due West to the circle of 22 
hours of Right Ascension, turns South towards 
Cygnus (Map xiii). 

54z. Andromeda — Mythologically the daughter 
of Cepheus and Cassiopeia, and bound to a rock — 
is represented on the globe with arms outstretched 
and fetters on the wrists. It contains 66 discerni- 
ble stars; Alpheratz — a — is in the head, Mirach 
— ,5 — in the girdle, and Almaach — y — in the 
right foot. (Sec. 51.) The right hand nearly 



touches Algenib. Nearly midway between a and 
/3 is d of the 3rd magnitude, in the right breast, 
forming one of a line of four stars, of which the 
most Southerly — C of the 4th magnitude — is in 
the right elbow, and the Northern one — - of the 
4th magnitude — is in the center of the breast. j9 is 
the most Southerly of three in the girdle. Nearly 
half way between y and Cassiopeia are No. 51 of 
the 3rd magnitude, and No. 54 of the 4th magni- 
tude, which mark the position of the left foot. 
The stars of the 4th magnitude — ?., /., and o -— 
Northwest of the figure, belong to Andromeda; 
o is in a line with, and North from, the West side 
of the Square of Pegasus. The Nebula 2° West 
of v, in the girdle, is visible to the naked eye. 10° 
Northwest from o is a Lacertas, of the 4th magni- 
tude, the only star of any note in the constellation 
called The Lizard. 

55. Pisces — The Fishes. This constellation 
lies South of Andromeda and the Square, cross- 
ing the Ecliptic, and lying between the circles of 
23 hours and 2 hours of Right Ascension ; it is 
represented as two fishes, connected by a long 
riband, and contains 113 discernible stars, but very 
few large enough to be easily found with the naked 
eye. Piscis Occidens — The Western Fish — 
lies North of the Equinoctial, and almost parallel 
with it, and Wcfst of the Equinox ; it contains six 
stars, as marked — j3 in the head, of the 5th mag- 
nitude, being 11^-° South of Markab, in a direct, 
line with the Western side of the great Square. 
Near to /? is y, the most Westerly of a row of three 
almost equidistant stars of the 4th magnitude, 
nearly parallel with the Southern side of the 
Square, and 8° North of the Ecliptic. Piscis 
Borealis, the Northern Fish, is parallel with the 
circle of 1 hour in Right Ascension, the head 
reaching to the girdle of "Andromeda, and the 
tail to the Ecliptic. It may be located by tracing 
the line of small stars from £, in the elbow of An- 



STAES NEAR THE VERNAL EQUINOX. 



19 



droraeda, Southeast to El Rischa (Sec. 52) — the 
third, marked p and 94, being visible as two stars 
of the 5th magnitude. The three following these 
are in the riband, the Ecliptic passing mid- 
way between o and it. At El Rischa — a Piscium 
— the riband turns West in a waving line to the 
tail of the Western Fish, crossing the Ecliptic on 
the first hour circle, the intersection being between 
e and e. The small square of stars South of the 
Equinox belongs to Pisces ; those in the extreme 
lower right hand corner are in Aquarius. The 
long line of prominent stars, Southeast of Pisces, 
are in Cetus. 

56. Aeies — The Ram. This Constellation — 
mythologically the Ram that bore the golden 
fleece — is East of Piscis Borealis, being repre- 
sented as recumbent on the Ecliptic, with one fore 
leg stretched out across the node of the riband of 
Pisces. It contains 66 discernible stars. From 
Hamal — a — of the 2nd magnitude (Sec 52) in the 
middle of the forehead, nearly 4° West, is Sheratan 
■ — fi — a pearly white star of the 3rd magnitude; 
and l£° South of /3 are two stars of the 4th mag- 
nitude — y 1 and y 2 — only 9" apart, and shown as 



one on the map. They are named Mesarthim. 
These are all the prominent stars in Aries. 16° a 
little South of East from a is d of the 4th magni- 
tude, in the hinder part of the animal, and it, e, Z 
and r — all of the 5th magnitude — near <5, com- 
plete the ill defined figure. The last named stars 
are shown in Map No. iv. 

57. Muse a — The Fly. Northeast from Hamal, 
and about the same distance from Algol, South- 
west, is a group of three stars — one of the 3rd 
magnitude, and two of the 4th — usually cata- 
logued as in Aries, but known as the Fly. There 
is another Musca near the South Pole, a very un- 
important constellation. 

58. Trianguli — The Triangles. The Star/3 
Trianguli (Sec. 52), of the 4th magnitude, lies at the 
Northern angle of a figure formerly marked with 
two triangles — now but one ; a — a yellow star of 
the 3rd magnitude, 7° from /?, and the same dis- 
tance from Hamal towards Cassiopeia, — maiks the 
Western Angle, and forms the vertex of an obtuse 
isoscles triangle, whose base, bounded by /? Trian- 
guli and a Arietis, is on the circle of 2 hours of 
Rio-ht Ascension. 



Define and explain (the figures refer to the sections) : 

48. Connection of Maps I. and II. 49. Equinoctial Colure extended ; Alpheratz ; Aigenib. 50. Square of Pegasus. 
61. Alpheratz to Mirfak ; Shining mile-stones. 52. Hamal ; El Rischa ; Mira. 53. Mirfak ; Algol ; Camelopardus ; Milky- 
Way. 54. Andromeda ; Alpheratz ; Mirach ; Almaach ; remarkable Nebula ; Lacerta. 55. Pisces, "Western and 
Northern ; elbow of Andromeda to El Rischa ; Aquarius ; Cetus. 56. Aries ; Hamal ; Sheratan ; Mesarthim ; South- 
east from Hamal. 57. Musca. 58. Trianguli. 



MAP NO. III. 



SO. This map covers nearly the same portion 
of the heavens as the preceding, but is differently 
projected, being arranged with the Ecliptic as the 
principal line, the curved lines running up and 
down the map being circles of Latitude, meeting 
in the Ecliptic Poles (Sec. 44). The Equinoctial 
runs obliquely ; the Square of Pegasus is in the 
upper right hand corner. Maps III. to X., inclu- 
sive, are constructed on this plan, enabling the 
student to trace out the paths of the members of 
the Solar System, and to refer them to the Solar 
Path, more readily than could be done on an Equi- 
noctial projection. (Sec. 27.) 

60. The Zodiac. The constellations which lie 
on the Ecliptic line are called the Zodiac, the word 
meaning "the circle of animals;" but it is now 
used also to indicate a baud of 16° in breadth, 8° 
on each side the Ecliptic. Some 2,300 years ago, 
the Zodiacal list was remodelled, and the twelve 
signs received the names they now bear, (Sec. 
23.) Each of those signs was then occupied by a 
group of stars bearing the same name, as : Aries 
then occupied the first 30° East from the Vernal 
Equinox, and to Pisces was allotted the 30° next 
West of that point. The Precession of the Equi- 
noxes (Sec. 25) has, since then, carried them back 
more than a whole sign over the constellations 
Pisces and Virgo, so that the stars then in the 
sign yi are now in °p, and those then in T13J are 
now in =a=. The number, twelve, was probably 
chosen because that was the nearest even repre- 
sentative of the number of new moons in the year. 

61. The first group was probably called "Aries'" 
because, at the time the Sun was among those 



stars the young of the flock were born : not be- 
cause the ancients fancied a resemblance to the 
shape of a sheep among the stars. It was a sym- 
bolic mode of recording a fact (Sec. 46). So, the 
place of the Sun, during that part of the year 
corresponding to the period now included between 
the middle of February and the 21st of March, 
was called Pisces, because that space marked 
the fishing season. There was also, perhaps, an 
allegorical reason for the latter in the singular 
paucity of notable stars in that part of the 
heavens, which might be considered as indicative 
of the poverty of fish diet. 

62. Cetus — The whale. This constellation 
occupies the Southern half of the map, lying South 
of Pisces and Aries, nearly parallel with the 
Ecliptic, the head on the Equinoctial, reaching 
into the middle of the sign b ; the tail extends to 
15° or 18° West of the Equinox. Cetus occupies 
nearly three hours in passing the meridian, its 
center being about half an hour later than Cassio- 
peia. It is seen in the Southern part of the 
heavens, about 30° from the horizon, about the 
same times that the Dipper is visible near the 
Northern horizon. It contains 97 discernible stars, 
including several of prominence. Mira — o Ceti — 
in the neck (Sec. 52) 7° Southeast from El Rischa, 
and in a direct line with the stars in that part of 
the ribaud nearest to Piscis Borealis, is a variable 
star, being sometimes of the 2nd magnitude, and 
at others so small as to be scarcely visible. It is 
on the circle which divides the signs °P and « 
and passes through /3 Andromeda?. Nearly 13 3 
East of Mira is Menkar — a — of the 2nd magni- 







. Map M>M * 








B 






f 


oasis 






* 

* 







B 













SOUTHEAST OF THE VERNAL EQUINOX. 



21 



tude in the jaw; 5, of the 4th magnitude, is be- 
tween o and a, and y, of the 3rd magnitude, is a 
little further North, and in a direct line between 
Menkar and El Rischa; y is the root of a line of 
three stars in the direction of /? Arietis ; 15° South 
of y, and about 10° from Mira, is a trapezium 
of small stars in the breast. A line from Menkar, 
through Mira, to the tail of Cetus, will take in 
and 7], both of the 3d magnitude ; and nearly half 
way between and the trapezium, is C of the 3d 
magnitude, named Baton Kaitos. Diphda — /? — 
of the 2nd magnitude, is very near the circle divid- 
ing the Signs T and X, with 21° of South lati- 
tude ; it is 40° distant from Menkar, nearly on the 
same line with Mira : Alpheratz forms the vertex 
of a triangle, having a and /3 Ceti at the angles of 
the base. 

63. Phcenix. A constellation called the 
Phoenix lies South of Cetus; it contains 13 dis- 
cernible stars, a, of the 2nd magnitude, in the neck, 
is shown on the margin ; it is situated 24° South 
of Diphda, and just East of the Equinoctial Colure, 
on a line with Megrez, Chaph, Alpheratz, and 
Algenib ; /?, of the third magnitude, is 8° South- 
east of a, and on the circle of 1 hour of Right 
Ascension ; y, of the 3rd magnitude, is 12° East 
of a, and 5° Northeast of ;?. 

64. Erldanus — The River Po. The stars 



under the neck of Cetus, in the lower left hand 
corner of the map, are in the constellation Eri- 
danus — a long, straggling assemblage of stars. 
The upper portion of the stream, shown on this 
map, is at the bend which connects the Northern 
and Southern portions of the constellation. The 
Northern part is shown entire in the next map ; 
the Southern stream stretches far towards the 
South Pole. (See Map No. xiv.) A line from the 
head of Aries, through Menkar, and produced 22° 
farther, will pass through Zaurak — y — of the 2nd 
magnitude, taking in S, of the 3rd magnitude, on 
the way ; from d a line of prominent stars stretches 
half way to Mira. Below the trapezium of Cetus 
are t 1 and r 3 , of the 4th magnitude, and lower, 
nearer Zaurak, is t 4 , of the 3rd magnitude. Be- 
yond these is the largest star in the constellation 
— a — of the 1st; magnitude, named Achernar; 
it is too far South to be shown on the map, or seen 
in the Northern States, being 58° South of the 
Equinoctial; it is 19° Southeast from a Pbcenicis, 
and 51° a little West of South from Zaurak. A 
little east, and 21° South of Zaurak, and 18° South- 
east of t 4 , is u 4 , with o 5 1° East of the latter. 
Theemin — l>i — is 5° Northeast from o 4 , in line 
with Achernar. u 5 is of the 4th magnitude, the 
other two are of the 3rd magnitude. 



Define and explain (the figures refer to the sections) : 

59. Map No. Ill ; the Square. 60. The Zodiac ; ancienffand modern ; changes ; effect of Precession. 61. Aries and 
Pisces. 62. Cetus, extent ; Mira ; Menkar, line to Sheratan ; Diphda. 63. Phoenix ; with Megrez. 64. Eridanus ; 
Zaurak ; Achernar ; Theemin. 



MAP NO. IV. 



65. This map shows a section of the heavens 
lying immediately East of that shown in Map No. 
III. ; and includes y, d, e, and f, Eridani ; a Ceti, [i 
Trianguli, and y Andromedae, in common with it ; 
also Musca and the head and body of Perseus in 
common with Map No. II. It takes in a section 
from the middle of the Sign tf , to a little past the 
first degree of 23, the Colure of the Summer Sols- 
stice. The Equinoctial is represented running 
obliquely, from 15° to 23^° South of the Ecliptic. 
The Right Ascension of the center of the map is 
about 4-| hours, and it passes the meridan 4^- hours 
after the Vernal Equinox. This portion of the 
heavens is more brilliant than any other of equal 
extent. 

66. Perseus — Mythologically, the deliverer 
and subsequent husband of Andromeda, and slayer 
of the Gorgon — is represented on the Globe as in 
the act of making a back stroke with his sword at 
the head of Medusa, which is behind him. The 
Sword is shown in Mip No. II. The constellation 
contains 59 discernible stars. Of the line of stars, 
r h y, a, and d (Sec. 53), only the Southern three 
are shown on this Map ; 0, of the 4th magnitude, 
in the neck, is 7° from y towards Almaach, and 
the same distance from a Persei, forming the 
vertex of an isosceles triangle with a and y ; i r of 
the 4th magnitude, lies between and a. About 
6° beyond d from Almaach, is //, of the 4th mag- 
nitude, in the left knee, and above it is X of the 4th 
in a line beyond a with i and 0. A line of stars, 
curving Southward, round Algol, several degrees 
to the East of that star, form the hinder leg of 
Perseus; C of the 3rd magnitude, the most South- 



erly, being 19° from Mirfak. Two stars of the 4th 
magnitude are here shown near Algol, in the head 
of Medusa, which will aid in locating it (Sec. 53). 
The Milky Way includes the whole of the body, 
and the forward 1 'g, of Perseus. 

67. Taurus— The Bull. This constellation is 
now the third in order of the Zodiacal band, lying 
directly East of Aries, the principal stars being 
in the Sign n. Only the front portion of the 
animal is represented on the globe, but the great 
length of the horns compensates for the curtail- 
ment of the body. It contains 141 discernible 
stars. South of f and o in the foot of Perseus, 
8°, and 19° below Algol,, is a well known group 
called the Pleiades, containing Alcyone — i? — a 
greenish yellow star of the 3rd magnitude, and 
five others, four of which are of the 5th magni- 
tude ; the stars in this group are a little nearer 
together than indicated on the map. West of the 
Pleiades, 8°, is the group of small stars in the 
hinder part of Aries (Sec. 56). Southeast from 
the Pleiades 14°, and 32° below Algol, through o 
Persei, also 26° from Menkar, is a pale rose 
colored star of the 1st magnitude, called Alde- 
baran — a — in the eye of the Bull; and 3° above 
it, in the direction of C Persei is e, of the 3rd 
magnitude, a and e form the top of a prominent 
V-shaped cluster called the Hyades, with y of the 
3rd magnitude in the angle, pointing towards 
Menkar. A line of smaller stars running from just 
below the V towards Menkar, with a lower line, 
nearly paralled with these, locate the legs of the 
Bull. A line from Menkar through Aldebaran, 
produced 15° farther, will strike the Ecliptic be- 



THEEE TO SIX HOURS EIGHT ASCENSION. 



23 



tween two prominent stars at the tips of the Bull's 
horns, situated 8° apart; El Nath — /9 — the most 
northerly, is a brilliant white star of the 2nd mag- 
nitude ; the Southern one is C, of the 3rd magni- 
tude. Three small stars, nearly in a line with those 
in the lower foot of Perseus, mark the tops of the 
head and ears. This constellation is supposed 
to have been named to mark the time of the year 
when the young of cattle are born. 

68. Auriga — The Wagoner. This constella- 
tion is represented on the globe as a mis-shapen 
man, with a g.oat under one arm, and a bridle in 
the other hand. The constellation lies East of 
Perseus, and North of the horns of Taurus, with 
the left foot resting on the tip of the North horn — 
El Nath — /3 Tauri — being common to both. The 
circle of 6 hours of Right Ascension forms its 
Eastern boundary ; it contains 66 discernible stars. 
A line 18° north from El Nath will strike a, a bril- 
liant white star of the 1st magnitude, in the right 
shoulder, and named Capella, the she goat, a 
Aurigae is also 35° East of Almaach, and 8° far- 
ther East is Menkalinan — /3 — a yellow star of the 
2nd magnitude in the left shoulder; 0, of the 4th 
magnitude, is 8° South of /?, in the left arm; 3, of 
the 3rd magnitude, in the head, is 10° North of /?, 
in line with 0. A line from d through a, produced, 
will pass between the Hyades and Pleiades, taking 
in its course t] and C in the groin, both of the 4th 
magnitude, and passing ;, of the 4th magnitude, 
in the right foot; t] and C are best memo- 
rized as forming the Northern and shortest 
side of a small trapezium ; A, of the 5th magni- 
tude, is on the line between Capella and El Nath, 
the latter being also at the lower corner of a com- 
pressed square of five stars. Nos. 132 and 136, 
Southeast of El Nath, belong to Taurus ; those 
East of Menkalinan belong to Auriga, but are 
generally spoken of as lying in the Telescope of 
Herschel. 



69. Orion — The Hunter. South of Auriga, 
and Southeast of Taurus, is the brilliant constella- 
tion, Orion ; represented on the globe with club 
upraised, and shield presented to meet the assault 
of the Bull. It contains 18 discernible stars. 
The most prominent feature in Orion is the Belt, 
sometimes called "The Yard Stick — a row of 
three stars of the 2nd magnitude, 3, e, and £, form- 
ing a line of about 3° in length; Mintaka — 3 — 
the most northerly of the three, is but 0° 23' 28" 
South of the Equinoctial, and 46^° South of a 
Auriga?. At right angles with the line of the belt, 
and nearly equi-distant from it, are two stars of the 
1st magnitude; Betelgueuse — a — an orange 
colored star in the left shoulder, 10° Northeast, 
and Rigel — /3 — a pale yellow star in the right 
foot, 9° Southwest of the belt. Near /?, towards the 
belt, is r of the 4th magnitude ; 1° from both a 
and 3, and 15° above ft, is y, a pale yellow star of 
the 2nd magnitude, in the right shoulder; and 17° 
from ^through the belt, is Saiph — /. — of the 
3d magnitude, in the left knee ; x is also 8° East of 
ft, y is 40° South of Capella, and a is 38° South of 
Menkalinan, these four forming a long parallelo- 
gram, the diagonals of which would nearly cross 
in El Nath. A line from the belt, through a, will 
touch two small stars in the left elbow, nearly on 
the 6 hour circle, and North of these are three 
small stars, marked /, in the club hand. Three 
small stars in a triangular position mark the head, 
and are at the vertex of a triangle whose base is 
formed by the shoulder stars. The shield is formed 
round a curved line of eight small stars, with y at 
the center of the curve, and the convex side 
towards Aldebaran. South 4° from C, in the belt, 
is a sextuple star marked t, at the end of the sword, 
and close to it is the celebrated Nebula in the 
sword. The stars east of the club hand are in the 
constellation Gemini ; those east of the body be- 
long to Monoceros — The Unicorn — a constella- 



24 



ASTRONOMY. 



tion composed of small stars, and not outlined on 
these maps. 

70. Rigel is the middle one of three adjacent 
stars, forming an arc — r Orionis, of the 4th mag- 
nitude, in the foot, and A of the 4th beyond, with ,6 
— Cursa — a topaz yellow, of the 3rd magnitude, 
a little above the three, and equidistant from them ; 
A and/3 are in Eridanus (Sec. 64) at the origin of 
the Northern stream, which runs West from the 
foot of Orion, parallel with the Equinoctial, and 
just below it, till it comes under the feet of the 
Bull, and then describes a semi-circle with the 
crown of the arch towards the South, taking in y, 
<), and £, and No. 17 — four important stars, almost 
in a right line, and shown on Map No. III. The 
Milky Way runs from Perseus, Southeast, through 
the lower part of Auriga, and crosses the Ecliptic 
at the beginning of the Sign ®, just including the 
club hand of Orion within its Western edge. 

71. Hydrus — The Water Snake. This con- 
stellation lies near the South Pole, and contains 10 
discernible stars. 5° South East of Achernar — a 
Eridani — is a Hydri, of the 3rd magnitude, and 



16° farther, in the same direction, is y, of the 3rd 
magnitude; 12° Southwest of y is /3, of the 3rd 
magnitude, 21° below Achernar, less than 12° from 
the South Pole, and only 1° degree East of the 
Equinoctial Colure on the same line with Alpheratz. 
South of a, 6°, is t], of the 4th magnitude, which 
forms an equilateral triangle with /? and y. (See 
Map No. XII.) 

72. Reticulum Rhomboid alis. — The Rhom- 
boidal Net. 20° East of Achernar, and 12° 
North of y Hydri, is a, of the 3rd magnitude ; j3, 
of the 4th magnitude, is 4° Southwest of a, towards 
f] Hydri. 

73. Doradus — The Sword-Fish. This con- 
stellation contains 6 discernible stars, lying East 
and North of the Net. 8° North of a Reticuli, 
and 24° East of Achernar, is a, of the 3rd magni- 
tude ; /5, of the 4th magnitude is 9° East of a Reti- 
culi, and 12° below a star of the 1st magnitude 
called Canopus. y, of the 4th magnitude, is 5° a 
little West of South from a Doradus, in a direct 
line with /? 11° farther. 



Define and explain (the figures refer to the sections) 

65. Map No. IY., connections ; Eight Ascension. 66. Perseus ; Sword ; isosceles triangle ; line in hinder leg ; Milky- 
Way. 67. Taurus; Pleiades; Alcyone; proportion; Aldeharan ; Hyades ; Bull's horns. 68. Auriga; El Nath; 
Capella; Menkalinan; Telescope. 69. Orion; Belt; Mintaka ; Betelgueuse ; Eigel; Saiph; the Shield; Sword nebula ; 
Monoceros. 70. Cursa; Northern stream of Eridanus; Milky Way. 71. Hydrus ; South Pole. 72. Reticulum 
Rhomhoidalis. 73. Doradus. 



MAP NO. V. 



74. This map shows the relative positions of 
the principal fixed stars lying within a distance 
of about 50° East of Orion, and the Northern part 
of Auriga; including Canis Major and Lepus — 
constellations farther South than the range of the 
preceding map. It shows, on its Western side, the 
stars Betelgueuse, Menkalinan, Amiga?, /x and v 
Geminorura, and No. 5 Monocerotis, in common 
with the preceding map. The Right Ascension of 
its centre is about 7^- hours, and it crosses the 
Meridian *l\ hours after the passage of the Vernal 
Equinox. It is much less thickly dotted with 
prominent stars than the preceding map. 

75. Gemini — The Twins. This constellation 
is represented on the globe as two youths, seated 
closely together ; they are named Castor and Pol- 
lux, from two stars of the same names, one in the 
head of each figure — marked a and /5 respectively. 
Gemini is the fourth in order of the Zodiacal con- 
stellations, is just East of the sixth hour circle, and 
contains 85 stars discernible with the naked eye. 
A line drawn Southeast from Menkalinan will pass 
through Castor 22° distant, and Pollux 5° farther. 
Castor — a — is really two white stars of the 3rd 
magnitude, but so near together as to be ordinarily 
seen as one. Pollux — /? — is orange colored, of 
the 2nd magnitude, 34° Northeast of Betelgueuse, 
and located on the right angle of a triangle whose 
hypothenuse is included by Menkalinan and Betel- 
gueuse. From the latter, 14° towards Pollux, is 
Alhena — y — a brilliant white star of the 2nd 
magnitude, and 1° northwest of y is /z, of the 3rd 
magnitude, only 0° 50' South of the Ecliptic, and 
3|° beyond the beginning of the Sign ®. From 



fi, 6°, towards Castor, is Mebsuta — e — a white 
star of the 3rd magnitude, lying at the Northern 
corner of a square formed by e, p., y, and C ; that 
square is prolonged by a and /3 into a parallelo- 
gram 20° long, and 5° to 6° in breath. Wasat — 
d — of the 3rd magnitude, lies 13^° East of /*, and 
is but a few minutes South of the Ecliptic ; y and fi 
are in a line of four stars indicating the position of 
the feet, two smaller stars at the Northern end 
curving towards the West, near the club hand of 
Orion. Equidistant about 4° from j3 are x and c, 
making with it an equilateral triangle, the three 
forming, with 3, a cross 9° in length and 5° in 
breadth. Tejat — y — of the 4th magnitude, is 2° 
West of ij. ; and No. 1, of the 5th magnitude, 2-|° 
West of rj, is named Propus, the name having 
been also given to x Aurigae, of the 4th magnitude, 
in the bridle of Auriga, and nearly in line with 
Wasat and Mebsuta. This constellation was 
probably named Gemini, because of the twin-like 
character of the season during which the Sun 
traverses the space formerly occupied by this 
group ; it has also been suggested that, as the 
figure was originally that of two kids, the name 
was given to mark the time when the young goats 
first appear. 

76. Telescopium Herschelitjm — North of 
Gemini and East of Auriga, is a. modern constella- 
tion, called the Telescope of Herschel (Sec. 68), 
containing several small stars, generally catalogued 
as belonging^ to Auriga ; they form a small trape- 
zium North of Castor, and a small triangle a little 
Southeast of Menkalinan. There are no important 
stars between these and the Pole. 



ASTKONOMY. 



77. Cancer — The Crab* East of Gemini are 
five stars of the 4th magnitude, which, with a few 
of the 5th magnitude, constitute all that is ordina- 
rily visible of Cancer, the fifth in order of the Zodi- 
acal twelve, though it contains 83 discernible stars. 
It is represented on the globe as a large Crab with 
numerous claws. A line from Castor, through Pol- 
lux, produced about 8°, will touch ^ 2 , just North of 
the Ecliptic, with ;x 2 , of the 5th magnitude, near and 
above it ; 9£° further Eastward is 8, a straw colored 
star of the 4th magnitude, also just North of the 
Ecliptic. A little more than 3° North of 8 is y ; 
these are called The Aselli, or The Two Asses ; 
nearly midway between the Aselli, but a little 
"West of the line joining them, is a nebulous clus- 
ter, visible to the naked eye on a favorable night, 
and called Praesepe, or the Beehive. Acubens — 
a — of the 4th magnitude, is 6° Southeast of 8. 
The four stars marked //, e, A, and z, Northeast of 
Cancer, are in the head of Leo. Cancer, formerly 
occupying the sign of the same name, was proba- 
bly so called because the Sun, when in that part 
of the heavens, had ceased his advance towards 
the North Pole, and appeared to be progressing 
with a crab-like motion — sidewise — parallel with 
the Equinoctial, and soon receded towards the 
South — the Crab being, till a recent date, said to 
walk backwards. 

78. Canis Minor— The Lesser Dog. This 
constellation, containing 14 discernible stars, lies 
South of Gemini, and Southwest of Cancer. Pro- 
cyon — a — a yellowish white star of the 1st mag- 
nitude, is 26° East of Betelgueuse, 18^-° Southeast 
of Alhena, and 18° almost due South of Pollux. 
Gomeisa — /9 — a white "star of the 3rd magnitude, 
is 4° Northwest from Procyon, the two being on a 
line parallel with one passing through the heads of 
the twins, and are nearly the same distance apart 
as are Castor and Pollux. These two are the only 
stars of any note in the constellation. South of 



Cancer and East of Canis Minor, is a bent line of 
four stars of the 4th magnitude — 8, e, C, and — 
and South of these is Alphard — a — of the 2nd 
magnitude. These are in the head and first fold of 
Hydra. Alphard is 8° South of the Equinoctial, 31° 
Southeast by East from Procyon, and 44° South- 
east from Pollux, in a line with Castor. 

79. Canis Major — The Greater Dog. This 
is a prominent constellation, but lying so far South 
that it is never seen far above the horizon in the 
Northern States. It contains 31 discernible stars ; 
all the prominent ones are shown on the map, 
though the figure of the Dog is not given entire. 
Sirius — a — a brilliant white star of the 1st mag- 
nitude, in the mouth, is 27° from Betelgueuse, 
25° below Procyon, and 33° below Alhena, with 
16£° of South Declination. Mirzam — /5 — of the 
2nd magnitude, in the paw, is 5^° "West of Sirius, 
and y, of the 4th magnitude — Muliphen — in the 
head, is 5° East of Sirius, all three on a line with 
Alphard. A line from the belt of Orion, through 
,?, and produced 14° farther, will pass through Ad- 
hara — e — of the 2nd magnitude; 16° from Sirius, 
in a line with Betelgueuse, and 5^ East of e is y — 
Aludra — of the 2nd magnitude; 5° above ij 
towards /5, is Wesen — 8 — forming a triangle with 
r/ and e. No. 22 is just above s towards 8. a, /?, f, 
and 7], form a figure nearly approaching to a long 
parallelogram. Sirius is familiarly known as "The 
Dog Star." 

80. Lepus — The Hare. This constellation lies 
directly South of Orion, and contains 19 discerni- 
ble stars. Below Rigel 11°, and a little West of 
9° South from Saiph, is Arneb — a — a pale yellow 
star of the 3rd magnitude. A little West of 3° 
South from a, is Nibal — ,3 — a deep yellow star 
of the 4th magnitude ; 4° Southeast from /5, and 
5° below «, is y; these, with 8, in the Eastern 
corner, form a trapezium, very similar in size and 
shape to the dipper of Ursa Minor; 7° Northeast 



SEVEN HOURS IN EIGHT ASCENSION. 



27 



of a, and 5° South of Saiph, is y, with £ and 6 
about 2° distant — one on each side. 

81> CoLUMBA Noachi — Noah's Dove. This 
constellation, not shown on the map, lies South of 
Lepus, and contains 10 discernible stars. South 
of Arneb 17°, South of the belt of Orion 33°, and 23° 
Southwest of Sirius, is Phact — a — of the 2nd 
magnitude ; 3° Southeast of a, is /?, of the 3rd mag- 
nitude, and 1° Northeast of ' p is y, of the 4th mag- 
nitude, Southwest of a, 2°, is e; these four stars 
make a small rhomboidal figure. 

82. Two stars of the 3rd magnitude, 4° apart, 
lying East of Canis Major — p and % — are in the 
beak of the prow of Argo — the ship. Tureis — p 
— is 21° Southeast from Sirius, and 25° Southwest 
from Alphard. The scattered stars between the 
two dogs belong to the untraceable constellation 
Monoceros — The Unicorn. The Milky Way runs 
diagonally across the groups shown on Map No. V. ; 
from the arm of Orion and feet of Gemini, be- 
tween the Dogs, taking in the Unicorn, and prow 
of Argo. 

A space of more than 60° in length from the 
feet of Cepheus to Cancer, and 25° in breadth, 
Northeast of Cassiopeia, Perseus, Auriga, and 
Gemini, is peculiarly bare of stars prominent 



enough to be readily recognized ; it contains 
scarcely a star of greater magnitude than the 5th. 
For this reason the space is not represented on the 
map, although astronomers have divided its stars 
into two constellations. The Lynx occupies a space 
about 35° by 17°, North of Gemini and Cancer, 
and East of Auriga. It contains but two stars of 
the 4th magnitude; these are situated 17° a little 
East of North from the Aselli (Sec. 77). The 
space North of Perseus, Auriga, and the Lynx, is 
filled up on the globe by the long figure of the 
Camelopard ; its hinder hoofs nearly touch the 
head of Auriga (See Map No. IV.), and its head 
rests on the circle of 12 hours Right Ascension, 
a few degrees from the Pole. Caraelopardalus 
contains four stars of the 4th magnitude, enu- 
merated as Nos. 2, 3, 9, and 10. Nos. 2 and 3 
are about 1° apart, and 6° Northeast from y Persei 
(Sec. 53). East 12° from these, and 15° above 
Capella, is No. 10; shown on the margin of Map 
No. IV. North 6° from No. 10, in line with Ca- 
pella, and 12° from Nos. 2 and 3, is No. 9. These 
four stars form an isosceles triangle, whose base is 
about half the height, its broken apex being direct- 
ed towards the head of Perseus, and its Southern 
side parallel with the Equinoctial. 



Defke axd explain (the figures refer to the sections) : 

74. Map No. V. ; Connections. 75. Gemini ; Castor and Pollux ; Alhena ; Mebsuta ; Wasat ; Propus. 76. Telesco- 
pium Herschelium. 77. Cancer ; Aselli ; Praesepe ; Acubens. 78. Canis Minor ; Procyon ; Gorneisa ; Alphard. 79. 
Canis Major ; Sirius ; Mirzam ; Muliphen ; Adhara ; Aludra ; Wesen. 80. Lepus ; Arneb ; NibaL 81. Columba 
Noachi ; Phact. 82. Argo ; Tureis ; Milky Way. The Lynx ; Caraelopardalus. 



MAP NO. VI. 



83. This map represents the constellations Leo 
and Ursa Major, both marked by many prominent 
stars ; also Leo Minor, the Head of Hydra, and 
one of the Hounds of Bootes. It includes a sec- 
tion of the Ecliptic next East of that shown in the 
preceding map, but represents principally stars 
North of the Ecliptic. The middle of the lower 
part — the beginning of the Sign TTQ. — has about 
10 hours of Right Ascension, but where the center 
line cuts the Dipper the Right Ascension is about 
12 hours, the hour circles being perpendicular to 
the Equinoctial, which is represented by the oblique 
line in the lower left. The map contains the head 
of Hydra, part of Cancer, and four stars in the 
head of Leo, in common with the one preceding it. 

84. Ursa Major — The Great Bear. This 
constellation lies nearly midway between the Equi- 
noctial and the Pole, and contains 87 discernible 
stars, including the Dipper (Sec. 38), which is situ- 
ated in the rear half of the body and the tail. 
The Dipper stars are named, nearly in the order 
of their Right Ascensions, thus : a — Dubhe — a 
yellow star of the 1st magnitude ; ,6 — Merak — a 
greenish white, of the 2nd magnitude ; y — Phecda 
— a topaz color, of the 2nd magnitude; 3 — Me- 
grez — a pale yellow, of the 3rd magnitude; s — 
Alioth, of the 3rd magnitude; C — Mizar — a bril- 
liant white of the 3rd magnitude : y — Alkaid, or 
Benetnasch — a brilliant white, of the 2nd magni- 
nitude. The small star above Alioth is named 
Alcor. The position of the nose of the Great 
Bear is marked by o, of the 4th magnitude, out- 
side the margin of the map ; o is 18£° from Dubhe, 
in a direct line with Alioth and Alkaid. Talita — 



i — of the 3rd magnitude, in the tore foot, is 20° 
from Merak, in a line with Megrez ; 0, of the 3rd 
magnitude, is 6^° above t in the same direction. 
The hind foot is marked by ? and v, both of the 
4th magnitude, f being 31° Southeast from c. Half 
way between £ and [i is <p, of the 3rd magnitude, 
in the hind quarter; /, of the 4th magnitude, is 
Northeast of 4\ and about equidistant from it and 
y. Nearly on a line with ? and :, and midway be- 
tween them, are p. and A, both of the 3rd magni- 
tude, and marking the place of the advanced hind 
foot. Nos. 23 and 29, in the neck, are easily 
located on lines from o to a and /3. 

85. Canes Venatict — The Hounds of Bootes 
— are East of Ursa Major ; the constellation con- 
tains 25 visible stars. A line from Dubhe, through 
Phecda, produced 19° farther, would touch a, of 
the 2nd magnitude, and named Cor Caroli — the 
" Heart of Charles." The star is located in the heart 
of one of two hounds named Asterion and Chara, 
which, under the guidance of Bootes, were sup- 
posed to follow the two Bears around the Pole. 
The hounds are technically known as Canes Ve- 
natici, but only Chara is shown on our maps, a 
and Alioth are pointers to the pole. 

86. Leo — The Lion. This is now the sixth in 
order of the Zodiacal Constellations ; it contains 
95 discernible stars, and is situated Eastward of 
Cancer, but is best located independently; or by 
reference to Ursa Major. It is represented on the 
globe as a huge animal with flowing mane, open 
mouth, and long tail; the body just North of the 
Ecliptic, and the hinder foot dipping below the 
Equinoctial. Regulus — a — a nearly white star 



THE GKEAT BEAR, AND THE LIONS. 



of the 1st magnitude, in the breast, called also 
" Cor Leonis," or the " Lion's Heart," is situated 
only 0° 28' North of the Ecliptic, in 28° 5' of the 
Sign Si, and 22£° Northeast by North from 
Alphard ; 5° North of a is y, of the 3rd magnitude 
and 8° 21' distant from a is Algeiba — y — a bright 
orange colored star of the 2nd magnitude, the line 
from which to a is perpendicular to the Ecliptic, 
and points directly to Phecda and Megrez, in the 
Dipper ; the distance from Regains to Megrez is 
51° 11'; 5j Leonis is equidistant from a and y, 
towards the West, and forms, with a, the handle, 
n the well known Sickle of Leo, which curves 
*ound to the West, forming the arch of the neck, 
md ends in the lower jaw. The Sickle consists of 
h V, Yi £ of the 4th magnitude, n and e, of the 3d 
magnitude, and A of the 4th magnitude ; x of the 5th 
magnitude giving the limit of the nose about 4° 
North of X. East from y 1 3°, is Zozma — d — a pale 
yellow star of the 2nd magnitude, in the back — 
lence sometimes called " Dorsa Leonis ; " d lies at 
the Northern end of a line of six stars, running 
iue South, 23° in length, which forms the axial 
ine of the hinder leg, and runs below the Ecliptic ; 
;he terminal star in the foot — e — of the 4th mag- 
nitude, is backed by u, of the 4th magnitude, 
1° distant, in direct line with a star of the 3rd 
magnitude, marked /3, named Zavijava, and be- 
longing to Virgo. The line from S extended 7° 
below e, will pass through 0, of the 4th magnitude, 



in the Crater. A line from y through y, will pass o, 
of the 4th magnitude, and $, of the 5th magnitude, 
in the fore legs. Acubens, in Cancer, is about 
8° West of the latter. The head of Hydra is 
Southwest of o aud ?. A line from Iiegulus to <r, 
of the 4th magnitude, the fourth star in the hinder 
leg, will pass near p and y,. both of the 4th magni- 
tude — the latter in the first hind leg. East of a, 
25°, and 10° Southeast from 8, is Denebola — /J — 
a bluish star of the 2nd magnitude, in the tail, 
and 13° above j3 Virginis, in direct line towards 
Phecda. The stars East of Leo belong to the 
constellation Virgo. The Sun was formerly 
among the stars of Leo during the latter part of 
July and the first two thirds of August. They 
were named after the Lion, probably as a symbol- 
ism to indicate the raging heat of that portion of 
the year. The Sickle is now with the Sun in the 
harvest season. 

87* Leo Minor — The Lesser Lion. This con- 
stellation lies between Leo and Ursa Major. It 
contains 53 discernible stars, but only 5 of any 
note ; those are all of the 4th magnitude, and form 
a trapezium which lies just below the hinder feet 
of the Bear, and a little farther above Leo, in a 
direct line between the Sickle and the Dipper. 
West of the trapezium and North of the Sickle, 
are two stars of the 4th magnitude, in the fore 
paws, but generally catalogued as belonging to 
the Lynx (Sec. 82). 



Define and explain (the figures refer to the sections) : 



83. Map No. 6; Contents; Connections. 84. Ursa Major; Dubhe to Alkaid ; Alioth ; Alcor; the nose; Talita ; the 
feet. 85. Canes Venatici ; Cor Caroli; the hounds; Pointers. 86. Leo; Regulus; Algeiba; the Sickle ; Zozma toe; 
Acubens ; Denebola. 87. Leo Minor ; trapezium. 



MAP NO. VII. 



88. This map represents that portion of the 
Zodiac lying next east of Leo, but extends farther 
South than the map preceding. The Right Ascen- 
sion of its center is about 13 hours ; of the North 
portion more, of the South part less, than 13 hours. 
The stars shown near the center are on the merid- 
ian 1 hour after the Dipper occupies the meridian 
above the Pole (Sec. 37). The crossing of the 
Ecliptic and Equinoctial circles at the Autumnal 
Equinox, is shown to the right of the center. The 
map contains Cor Caroli, Denebola, with the 
stars in the hinder foot of Leo> the head of Virgo, 
and the West side of Crater, in common with Map 
No. VI. 

89. Virgo — The Virgin. This constellation 
is represented on the globe as a winged female, 
located parallel with, and principally North of, the 
Ecliptic, with the Equinoctial running diagonally 
through the figure ; she has a bundle of grain in 
her hand, supposed to have been gleaned in the 
harvest field. It contains 110 discernible stars. 
Zavijava — ,3 — a pale yellow star of the 3rd mag- 
nitude, is 13° South of Denebola, and near the 
Ecliptic, at the tip of the lower shoulder; 18° 
nearly East from Denebola, in line with d Leonis, 
is Vindemiatrix — e — of the 3rd magnitude; 8° 
belew e, 16° East of Zavijava, and nearly at the 
same distance North of the Equinoctial, is d, a 
golden yellow star of the 3rd magnitude ; 8° East- 
ward from Zavijava, is tj, of the 3rd magnitude, 
and nearly the same distance North of the Ecliptic. 
These five — ,3, r h 8, and e Virginis, and /? Leonis — 
form nearly a square, with the Southeast corner 
broken on the line joining rj and d. Two stars — o 



and v — of the 4th magnitude, lying obliquely across 
the line joining the two /S's, are in the head of Virgo, 
with - and ?, of the 5th magnitude, near them. 
South of East from Zavijava, 27°, is a — a clouded 
white star of the 1st magnitude, named Arista, and 
sometimes called " Spica," or " the Spike of the 
Virgin ;" it lies just South of the Ecliptic, 35° from 
Denebola, and 50° almost due South from Cor Ca- 
roli ; the distance from a to /? Virginis, is nearly the 
same as that from j3 Leonis to Cor Caroli. No. 61,. 
of the 4th magnitude, 7£ °below Arista, marks the 
tip of the Southern wing; and 0, of the 4th mag- 
nitude, nearly on a line between Arista and <J, gives 
the location of the hand. A line from /?, passing 
a little South of d, and produced 17° farther, will 
touch r, and 11° still farther is No. 109, both of 
the 4th magnitude, in the North Skirt ; C, nearly 
on the Equinoctial, between d and r, is 11° above a. 
South 7£° from No. 109, crossing the Equinoctial, 
is p., of the 4th magnitude, in the North foot, and 
10° Southwest from ;x is >*, of the 4th magnitude, in 
the right foot, near the Ecliptic, and 14° from 
Arista. The Virgin was supposed to represent 
the season of harvest. 

90. East of Denebola 36°, Southeast of Cor 
Caroli, 26°, and nearly 33° from Arista, on the 
same line of Longitude, is Arcturus — a ruddy 
yellow star of the 1st magnitude — a, in Bootes. 
The Ecliptic is perpendicular to the line joining 
Arista and Arcturus. These two, with Denebola 
and Cor Caroli, form what is sometimes called the 
Diamond of Virgo. The three first named form 
nearly an equilateral triangle, while Cor Caroli is 
at the right angle of a triangle with Arcturus and 



NEAR THE AUTUMNAL EQUINOX. 



31 



Denebola. From Arcturus, 5|° towards Denebola, 
is r, Bootis, of the 3rd magnitude, and 8° on the 
other side of Arcturus, is f, also of the 3rd mag- 
nitude; the star outside the map — ^ Serpentis — 
is 22° beyond Arcturus, in the same line. ? is the 
most Northerly of a line of three stars, in the left 
leg of Bootes, all of the 3rd magnitude ; the line is 
6° in length towards the feet of Virgo. 

91. Coma Berenices — The Hair of Berenice. 
This constellation lies north of Virgo, between it 
and Canes Venatici. It contains 43 discernible 
stars, but only 3 of the 4th magnitude, a and No. 
36 are easily found, being on a line midway be- 
tween Denebola and Arcturus, and about 3° asun- 
der. No. 23 is West and a little North from No. 
36, forming with it, and a, an obtuse triangle. 

92. Crater — The Cap. This constellation 
lies Southwest of Virgo, and South of the tail of 
Leo, and contains 21 discernible stars. The line 
in the hinder leg of Leo (Sec. 86), continued 7° 
from e Leouis, will touch in the Crater, and 8° 
farther is J, both of the 4th magnitude. From 
r t Virginis, through d Crateris, and 6° farther 
South, is o, of the 3rd magnitude, and 6° still far- 
ther is Alkes — a — an orange colored star of the 4th 
magnitude. Southeast 5° from a, is ,3, of the 4th 
magnitude, perpendicular to the line from a to 0; 
y, a bright white star of the 4th magnitude, equi- 
distant from a and ,3, is in a line from [3 towards 0. 

93. Corvus — The Crow. This constellation 
is East of Crater, and South of Virgo. It con- 
tains 9 stars visible to the naked eye ; 6 of these 
are easily recognized as forming a peculiar dia- 
mond figure of 4° to 6° on a side, with a promi- 
nent star at the Southeast and Northwest angles, 
and a pair of smaller stars at each of the other 



angles. Alchiba — a — of the 4th magnitude, in 
the beak, the most Southerly star in that corner, is 
on the Equinoctial colure, 2*7° from Zavijava, 
almost in direct line with Denebola, and 23° South- 
west from Arista ; /?, of the 2nd magnitude, is 6° 
East of a, towards the feet of Virgo. 

94. Hydra — The Snake. This constellation 
lies South of the Ecliptic, winding irregularly 
from below Cancer to opposite Libra; it is about 
100° in length, and contains 60 discernible stars. 
Crater and Corvus rest on the body, near the 
middle. The arc of four stars in the head, with 
Alphard in the first fold, are shown on Map No. 
V (Sec. 78). From Alphard to Alkes — a Crateris 
— is 24°, and the forward or Western part of the 
body of Hydra is almost a straight line between 
these two points; ,u, of the 4th magnitude, is 16° 
from Alkes, towards Alphard, and 6° farther West, 
almost equidistant from /jl and a Hydra?, is I, of the 
4th magnitude, the only star in Hydra of any con- 
sequence not shown on the maps. From Alkes, 
some distance East, the position of the body is 
best traced by reference to the stars in Crater and 
Corvus. Just under the tail of the latter, 8° and 
10° East from ,3 Corvi, in a line with s, and just 
below the end of the Southern wing of Virgo, are 
<!> and y, both of the 4th magnitude; 11° from y> 
and 18° below Arista, is -, of the 4th magnitude, 
in a line with Arista and d Virginis. 

95. A line from Cor Caroli through Arista, and 
produced 23° farther, will pass through the head 
of the Centaur, the upper part of which constella- 
tion contains a group of stars similar in arrange- 
ment to that in Corvus, but composed of larger 
stars. ;, of the 3rd magnitude, in the shoulder, is 17° 
Southeast from ,3 Corvi, nearly in a line with y Corvi. 



Define and explain (the figures refer to the sections) : 

88. Map No. 7; Connections. 89. Virgo : Zavijava; Vindemiatrix ; broken square; Arista; north Skirt. 90. Arc- 
turus; diamond of Virgo; left leg of Bootes; 91. Coma Berenices ; obtuse triangle. 92. Crater; Alkes. 93. Corvus; 
diamond ; Alchiba. 94. Hydra ; Alphard to Alkes. 95. Head of Centaur. 



MAP NO. VIII. 



90. This map comprises a section of the 
heavens next East of that shown in the map pre- 
ceding, the Ecliptic running nearly through the 
middle of the map; but, as this part of the Eclip- 
tic is far south of the Equinoctial, the stars shown 
near the lower margin are never seen far above 
the horizon of the Northern States. The map 
shows the constellations Libra, Scorpio, Ophiucus, 
and Lupus ; with portions of Hydra, Centaurus, 
Telescopium, Taurus Poniatowski, and Ara. It 
includes, in common with the preceding map, 
8 and ,<5 in the head of the Serpent, m and A in the 
feet of Virgo, « 8 Librae, - Hydra;, and t, ft, v, and 
Ceutauri, with a few smaller stars. The Right 
Ascension of the center of the map is about 16 
hours, and it is on the Meridian that number of 
hours after the Dipper is below the Pole (Sec. 36). 
The Stars in the upper left hand corner are very 
near the 18 hour circle, which runs through the 
beginning of V3. 

97. Libra — The Balance. This is the eighth 
in order of the Zodiacal constellations ; it lies East 
of Virgo, South of the Equinoctial, and on the 
Ecliptic, the greater number of its stars lying be- 
tween those two circles. It contains 51 discerni- 
ble stars. Zubenesch — a 2 — a pale yellow star of 
the 3rd magnitude, lies just North of the Ecliptic, 
8° from A, in the South foot of Virgo, 21° East 
from Arista, and 11° South from,u Virginis, forming 
with A and //, a nearly isosceles triangle, whose base 
is half the height. East from fi Virginis 9°, in line 
from Vindemiatrix, is Zubenelg— /3— a pale emerald 
colored star of the 2nd magnitude; a- and fi form 
with m and A Virginis, a nearly diamond trapezium ; 



and 5, of the 4th magnitude, 4° West from /?, 
towards Arista, forms a smaller trapezium with 
the other three. No. 37, of the 4th magnitude, is 
about as far East from ,3; and No. 51, of the 4th 
magnitude, in the Eastern edge of the constella- 
tion, is H° still further East, being 12° from /?. 
Southwest by South from No. 51, are two stars, of 
the 4th magnitude — 0, 6° below; and from two 
other stars of the 4th magnitude — >j and y— run 
West nearly 5° towards d, while Z, of the 4th mag- 
nitude, is 2|° Southwest, and 10° farther, in the 
same line, is No. 20, of the 3rd magnitude, in the 
Southern limit of the Scales. A few stars of the 
5th magnitude, lying near these, will be easily 
located. 

The step-like arrangement of Nos. 51 and 
48, and 0, r h r , C, and No. 20, is readily recog- 
nized in the heavens, though the stars are only of 
the 4th magnitude, ft Serpentis forms, with Zu- 
benelg and Zubenesch, a line of equidistant stars 
stretching from 2° South of the Equinoctial to the 
Ecliptic. The constellation Libra was so named 
because when the Sim formerly entered that group 
of stars the days and nights were equally balanced. 
Libra is the most modern of the ancient constella- 
tions ; on the earlier Zodiacs the claws of the Scor- 
pion were extended to the feet of Virgo. 

98. Scorpio — The Scorpion. This is the 
ninth of the Zodiacal constellations ; it is situated 
Southeast from Libra, and contains 44 discernible 
stars. It is recognized from the peculiar arrange- 
ment of the stars in the Southeastern portion. 
The principal star, Antares — a — a fiery red star 
of the 1st magnitude, is 46° Southeast by East from 



THE SCALES, AND THE SCORPION. 



33 



Arista, and 56° Southeast from Arcturus. It is 
located near the middle of the body, and henc,e 
is often called " Cor Scorpio" — the heart of the 
Scorpion. 

Nearly equidistant from a, in line with Arctu- 
rus, are Gramas — /? — a pale white star of the 
2nd magnitude, above, and e of the 3rd magnitude, 
below a ; 2° on each s de of a are a, of the 4th 
magnitude, and r, of the 3rd ; two smaller stars 
also lie near /?. From these, e, ft. 1 , n % , C 1 , ? 2 , r h 
6, i, z, u, and X, run in the order named, forming 
the tail, and describing nearly three-fourths of an 
ellipse. They are all of the 3rd magnitude ; Le- 
sath — X — in the extremity of the tail, is 19° 
Southeast of Antares in line with Zubenelg. The 
claws contain many stars of the 4th magnitude; ?, 
p, -, and <5, forming a line of 12° in length, run- 
ning due South from the head. The position of 
4', of the 5th magnitude, in the upper forward 
claw, is best noted by remembering that it is 3° 
East from No. 51 Libras — the uppermost star in 
the step of Libra. Scorpio was probably so 
named to memorize the fact that when the Sun 
was among those stars, the diseases of Autumu 
were prevalent. The positions of the stars are, 
however, naturally suggestive of the shape chosen. 

99. The tail end of Hydra is shown below 
Libra; it contains no prominent star not already 
noted. Farther South are the head and upper 
part of the body of Centaurus (Sec. 95). The two 
stars of the 3rd magnitude, at the Eastern end 
of the figure, are * Centauri and ,? Lupi ; they 
are about 1° apart, and 26° and 27° South of 
Zubenesch, 37° Southeast of Arista, and 24° South- 
west of Antares. Between Centaurus and Scorpio 
is Lupus — the Wolf. (See Sec. 134.) North- 
east of the tail of Scorpio is Telescopium. (See 
Sec. 113.) 

100. Aea — The Altar. This constellation lies 
South of the tail of Scorpio, and contains 9 dis- 



cernible stars, a Arae is 13° South of Les th; ,3 
and y are in the same line 6° and 7° farther South, 
and C and £ lie West of p and y ; all these, except 
e, are of the 3rd magnitude. 

101. Teiangulum Austkalis — Three stars, 7° 
8° and 6° apart*— a, of the 2nd magnitude, and /? 
and 7, of the 3rd, form the Southern Triangle. It 
lies 10° Southwest by South of ,3 Arse, and 8° 
East of a Centauri. (See Maps XII. and XIII.) 
The constellation contains 5 discernible stars. 

102. Ophiucds et Serpens — The Serpent and 
his Bearer. This constellation is North of Libra 
and Scorpio. It occupies a large space in the 
heavens, and contains 138 discernible stars, of 
which 74 are catalogued as in Ophiucus, and 64 as 
in Serpens. /? — a pale blue star of the 3rd mag- 
nitude, in the head of the Serpent, is 31° East of 
Arcturus, and with y, of the 3rd magnitude, 2° 
East, and No. 34, of the 4th magnitude, above, 
forms a small triangle in the head; with No. 38, 
of the 5th magnitude, they mark the location of 
the head. Unukulhay — a Serpentis — a pale yel- 
low star of the 2nd magnitnde, is 9° South fiom ,3, 
25° Southeast by East from Arcturus, and 34° 
Northwest by North from Antares; 3 — a bright 
white star of the 3rd magnitude in the first coil — is 
4° above a, towards the upper part of Bootes ; and 
3° below a is <t, of the 3rd magnitude, with A, 
of the 4th, just East of a. Southeast from a, 
are d — Yed — and e Ophiuci, both of the 3rd 
magnitude, and 1° apart, in the right hand of 
Ophiucus, in line with a and e Serpentis. The 
Serpent now winds back around the arm, taking 
in one star of the 4th magnitude, and two of the 
5th, and then stretches Southeast across the body, 
taking in -q Ophiuci, of the 2nd magnitude, 17° 
beyond e, in line with a; then winds up Northeast, 
including o, v and -q, of the 4th magnitude, 5° and 
9° apart. The tail extends some distance farther 
than the limits of the map, but only contains one 



34 



ASTRONOMY. 



other noteworthy star — 0, of the 4th magnitude, 
about 11° beyond ^. East of /3 27°, nearly on a 
line with Arcturus, and 28° a little North of East 
from Unukulhay, is Rasalague — a Ophiuci — in 
the head, a Sapphire colored star of the 2nd mag- 
nitude ; 8° below a Ophiuci is Celbelrai — /3 — of 
the 2nd magnitude, in the left shoulder, in line 
towards v Serpentis, with y, of the 4th magnitude, 
about 2° farther in the same line. The right 
shoulder is marked by x and j, both of the 4th 
magnitude, 13° from fi towards the head of Ser- 
pens, and with ,3 forming a triangle with Rasalague. 
£, of the 3rd magnitude, in the right knee, is 21° 
below x and i, towards Antares. The lower part 
of the right leg is marked by a line of three small 
stars below C, extending nearly to /3 Scorpii, the 
lowest — d> — being 10° from C The left leg con- 
tains £, of the 4th magnitude, 6° below -q, and 4° 
farther .are three stars in. the foot, including 0, of 
the 3rd magnitude, 12° East of Antares. 

103. The group of stars 5° Southeast of the 
left shoulder of Ophiucus, are in the face of Tau- 
rus Poniatowski. West of Rasalague 5°, is Ras 
Algethi — a — an orange colored star of the 3rd 
magnitude in the head of Hercules; and 14° far- 
ther West are /? and y Herculis, two silver white 
stars of the 3rd magnitude, 3° apart, the line pass- 



ing through them pointing to Unukulhay. East 
and a little North from Arcturus, 20°, is Alphecca 

— a — Corona? Borealis — a brilliant white star of 
the 2nd magnitude, 21° North of Unukulhay, and 
14° from $ Herculis, in line with Rasalague. 

South of the body of Scorpio, between Ara 
and Lupus, and North of Triangulum Australia, is 
a space about 10° broad, and 25° in length from 
North to South, which has been filled in by modern 
astronomers with the figure of a squaring tool and 
ruler, and called Norma Euclidis — the Square of 
Euclid — in honor of the great geometrician. It 
contains no important stars. Immediately South 
of 'Lupus, and West of Triangulum, is another 
small geometrical constellation called "Circinus" 

— the compasses. This constellation contains but 
one important star — a, of the 4th magnitude, and 
shown on Map XIII., at the feet of Centaurus. 

The Milky Way skirts the region represented near 
the left margin of the map ; through the head of 
Taurus Poniatowski in a narrow stream, and takes 
in the left shoulder and arm of Ophiucus to the 
first two joints in the tail of Scorpio, there uniting 
at the bend of the tail with another stream which 
includes the extremity of the tail of Scorpio, and 
flowing through Ara in one broad stream; then 
North of Triangulum, and through Circinus. 



Define and explain (the figures refer to the sections) : 

96. Map No. VIII. ; connections. 97. Libra ; Zubenesch ; Zubenelg ; diamond ; the step. 98. Scorpio ; Antares ; 
Graffias; course to Lesath ; upper forward claw. 99. Centaurus and Lupus. 100. Ara. 101. Triangulum Australis. 

102. Ophiucus et Serpens; triangle in head; Unukulhay; Yed ; Eta; Rasalague; Celbelrai; right shoulder ; the legs. 

103. Taurus Poniatowski ; Alphecca ; Norma Euclidis ; Milky "Way. 



MAP NO. IX. 



104. This map represents a section of the 
heavens next East of that shown in the preceding 
map; its center has a Right Ascension of about 
19 hours, and comes to the meridian about 5 hours 
before the Vernal Equinox. It contains, in com- 
mon with Map No. VIII., the left shoulder and 
head of Ophiucus, the tail end of Serpens, the tail 
of Scorpio, and the principal stars in Ara. 

105. Taurus Poniatowski — The Bull of 
Poniatowski — is a small constellation, containing 
only 5 noteworthy stars, located East of the left 
shoulder of Ophiucus, and catalogued as belong- 
ing to that constellation. Three of those stars are 
of the 4th magnitude, and form a small triangle 
5° Southeast of Celbelrai. 

106. Aquila et Antinous — The Eagle and 
Antinous. This constellation lies on the Equinoc- 
tial, East of the body of Ophiucus, and contains 
74 discernible stars. East 32° from Celbelrai, 34° 
from Rasalague, and 8° North of the Equinoctial, 
is Altair — a — a pale yellow star of the 1st mag- 
nitude, in the neck of the Eagle, and the middle 
one of three prominent stars ; y, 2° above, and /?, 
3° below, both pale orange stars of the 3rd magni- 
tude ; 8° farther Southeast by South, in the line of 
these, is 0, of the 3rd magnitude, in the hand of 
Antinous; Southwest from Altair 9°, and 12° from 
0, is d, of the 3rd magnitude, making a triangle 
with a and 0, also- with /? and y ; 9° below S, in a 
line from y, is A, of the 3rd magnitude, in the heel 
of Antinous ; tj, of the 4th magnitude, is in line 
between and d, the Equinoctial passing nearly 
midway between i) and 0. The two stars of the 
5th magnitude, Southwest of />., belong to an ob- 



scure constellation called " Clypei Sobieski" — the 
shield of Sobieski — not outlined on the map. 

107. Delphinus — The Dolphin. This con- 
stellation lies East of Aquila, and contains 18 
discernible stars. Nearly Northeast 14° from 
Altair, is Svalocin — a — a pale white star of the 
3rd magnitude, situated at the Northern side of a 
small diamond figure of stars, about 2° apart. 
Rotanen — /? — a green tinted star of the 4th mag- 
nitude, is at the Southwest corner of the figure ; 
5° South from Svalocin, is e, on a line drawn 
through Rotanen. 

108. Sagittarius — The Archer. This is the 
tenth in order of the Zodiacal constellations, lying 
East of Scorpio, South of the Ecliptic, and on the 
Solstitial colure, or 18 hour circle; it contains 69 
discernible stars, and is represented on the globe 
as a Centaur — half man and half horse — with 
bow and arrows, his head on the Ecliptic The 
most prominent stars are four of the 3rd magni- 
tude — <S, e, ?, and <t, forming a rhomboid, or elon- 
gated diamond figure, about twice as long as 
broad; d, in the hand, is 25° due East from An- 
tares, and 9-|-° beyond, in the same line, is f, in the 
breast, the line joining them being the shortest diag- 
onal of the rhomboid ; e is 5° below d, and about 
10° from the end of the tail of Scorpio ; <r, in the 
forward shoulder, is 5° above ?. North 9° from 3, 
11° Northwest from <7, and 16° Southeast from tj in 
the left knee of Ophiucus, is //., the last of a slightly 
curved line of nearly equidistant stars, composed 
of Unukulhay, Yed, yj Ophiuci, and p. Sagittarii. 
y 1 and y 2 , both of the 4th magnitude, nearly 3° 
West of <J, are in the crown of the bow. 



36 



ASTRONOMY. 



The place of the head of Sagittarius is marked 
by three stars of the 4th magnitude, 5° above a, 
and just North of the Ecliptic; a, of the 4th mag- 
nitude, is 12° nearly South from C, on a line with 
a\ 5° below a are fi 1 and /3 2 , of the 4th magnitude, 
in the forward leg. The only remaining star of 
note in the constellation is c, of the 4th magnitude, 
14° East from C, in line with d. The constel- 
lation Sagittarius was probably so named because 
the Sun was formerly passing through it at the 
season for hunting in the East. 

109. Corona Australis — The Southern 
Crown. Northwest 4° from a Sagittarii, is a Coro- 
na? Australis, of the 4th magnitude, in a curved 
line of four stars on the Eastern side of the con- 
stellation. 

1 10. Microscopium — The Microscope. South- 
east 12° from c Sagittarii is a Microscopii, of the 
4th magnitude, nearly between the hind feet of 
Sagittarius ; it is the only star of note in the con- 
stellation. 

111. Grus — The Crane. Southeast 14° from 
a Microscopii, in line with c Sagittarii, is y, of the 
3rd magnitude, in Grus; 10° South from y is a 
Gruis, of the 2nd magnitude ; /3, of the 3rd mag- 
nitude, is 6° East from a. 

112. Indus et Pavo — The Indian and Pea- 
cock. South 14° from a Microscopii, is a Indi, of 
the 3rd magnitude, forming with it and a and y 
Gruis, a nearly square figure. South 10° from a 
Indi, is a Pavonis, of the 2nd magnitude, in the 
eye of the Peacock ; and 10° South from a Pavonis, 
is ;3 Pavonis, of the 3rd magnitude — the middle 
one of a line — <J of the 4th magnitude, and ft and 
y of the 3rd magnitude ; the line is 8° in length, 
and runs East and West on the Antarctic circle ; 



therefore not visible in the United States, a Pa- 
vonis is 25° East from /3 and y Arse, and 35° 
Southeast from Lesath. a Pavonis, a Indi, and a 
and y Gruis, form a large diamond figure. Indus 
et Pavo is a double constellation, like Aquila et 
Antinous, and extends nearly to the South Pole. 

113. Telescopium — The (Southern) Telescope. 
Between a Pavonis and X Scorpii, and between 
Sagittarius and Ara, is a group of stars in the 
middle of the Southern Telescope — a, s, and C — 
all of the 4th magnitude, and forming a small 
triangle, a forming also a smaller triangle with 3 1 
and <5 2 , of the 5th magnitude, /j. Telescopii, of 
the 4th magnitude, is 14° below a, towards a Pa- 
vonis ; and y, of the 4th magnitude, is 3° East of 
Lesath, and 12° above a ; j3 is 6° East of y. 

111. A little East of South, 25° from Altair, 
and 23° a little North of East from a Sagittarii, in 
line with 8, is Dabih — /3 — an orange tinted star 
of the 3rd magnitude, in the head of Capricorn ; 
2^° above Dabih is Secunda Giedi — a 2 — a pale 
yellow star of the 3rd magnitude, and just above 
a 2 , is Deshabeh — a 1 — of the 4th magnitude, also 
called "Algedi;" 12° below /3, and 10° East from 
c Sagittarii, is <p, of the 4th magnitude, in the 
knee of Capricorn. 

The main stream of the Milky Way comes with- 
in the limits of the map at the lower right hand 
corner, including Ara and the tail of Scorpio. At 
the tail it divides into two narrower streams ; the 
Eastern one takes in the bow of Sagittarius, 
shield of Sobieski, the feet of Antinous, and skirt- 
ing his back, bends to include the whole of Aquila; 
the Western stream includes the left foot, hand, 
and shoulder of Ophiucus, with a part of the tail 
of Serpens, and Taurus Poniatowski. 



Define and explain (the figures refer to the sections) : 

104. Map No. IX ; connections. 105. Poniatowski's Bull. 106. Aquila et Antinous ; Altair ; Clypei Sobieski. 107. 
Delphinus ; Svalocin ; Rotanen. 108. Sagittarius ; Rhombus ; Unukulhay to Mu ; the bow. 109. Corona Australis. 
110. Microscopium. 111. Grus. 112. Indus et Pavo. 113. Telescopium. 114. Secunda Giedi ; Algedi; Milky Way. 



MAP NO. X. 



115. This map represents a section of the 
heavens next East of that shown in the map pre- 
ceding; the Right Ascension of its center is about 
22 hours, and it comes to the meridian above the 
earth 2 hours before the Vernal Equinox, and a 
little more than half way from the Zenith towards 
the Southern horizon. It contains, in common 
with Map No. IX., the heads of Aquila et Antinous, 
Delphinus, the head of Capricorn, stars in the 
hand of Aquarius, a Microscopii, and y Gruis. 

116. Capricor^us — The Goat. This is the 
eleventh in order of the Zodiacal constellations, 
and contains 51 discernible stars. It lies on the 
Ecliptic, East of Sagittarius, and is represented 
on the globe as a goat with the tail of a fish. The 
principal stars are those already named (Sec. 114) 
— ,<9 in the head, and a* and a 2 , in the left horn. 
Below ,5, 4°, are it and p, both of the 5th magni- 
tude, in the lower part of the face; 21° East from 
,9 is 8, of the 3rd magnitude, in the tail, and 2° 
"West of 8 is y, of the 4th magnitude ; £ , of the 4th, 
is 8° South from 8, and 10° a little North of East 
from (p in the knee (Sec. 114) ; /. and e, of the 5th 
magnitude, between 8 and C, and fi, of the 5th, 
a little North of 8, form a line marking the posi- 
tion of the tail, and its junction with the next con- 
stellation ; the line points towards a Microscopii. 
Capricornus was probably so named to signify that 
when the Sun was among those stars he began to 
move upwards, towards the North, the goat being 
a climbing animal. The fish tail was a later myth- 
ological addition. 

117. Aquarius — The Water Bearer. This is 
the twelfth in order of the Zodiacal constellations ; 



it lies on the Ecliptic, East of Capricorn, West of 
Pisces, and contains 108 discernible stars. It is 
represented as a man in nearly a sitting posture, 
with an inverted urn in his grasp, from which flows 
a stream of water. The two principal stars are 
both of the 3rd magnitude, and a pale yellow color, 
one in each shoulder. Sadalsund — ft — is 20° a 
little North of East frorn Dabih ; and Sadalmelik 
— a — is 10° farther in the same line, also 21° 
Southwest from Markab, in the Square of Pegasus 
(Sec. 50), nearly on a line with Alpheratz, and 
about as far distant from Markab as is that star ; a 
is also 29° East from 6 Aquilse, and, with it, marks 
very nearly the course of the Equinoctial. Sadal- 
sund is 25° Southeast from Svalocin. Midway 
between Deshabeh and Sadalsund are ;j. and <?, of 
the 4th magnitude, in the hand, and 4° North from 
these is No. 3, of the 4th magnitude, nearly on the 
line between Sadalsund and Aquilse ; 20° South- 
east from a, and 16° East from 8 Capricorni, is 
Scheat — 8 — of the 3rd magnitude, in the for- 
ward knee ; 6 and £, of the 4th magnitude, 7° 
apart, lie nearly midway across the liue from y? to 
8; 1° a little East of South from 8 is c 2 , of the 
4th, with c 3 , of the 5th magnitude, marking the 
position of the forward foot. 

East 6° from a is C, of the 4th magnitude, the 
central star in a Y-shaped figure formed by y, of 
the 3rd, C, t], of the 4th, and it, of the 5th magni- 
tude — the top towards a — and marking the place 
of the Urn. The course of the Stream is marked 
by a number of small stars almost in a semicircle 
round the knee and feet of the figure ; A — the 
only star of the 4th magnitude in the stream — 



ASTEONOMT. 



is 10° from y in the Urn, and 20° East from ,?. 
East 13° from c* is No. 2 Ceti, in the tail of Cetus 
(Sec. 62). East 12° from the middle of the T is 
r Piscium, of the 4th magnitude, in the head of 
the Western Fish. (Sec. 55.) The constellation 
Aquarius, probably received its name from the fact 
that the rainy season was coincident with the 
course of the Sun among those stars. 

118. Piscis Attstbaijs — The Southern Fish. 
This constellation is South of Aquarius, and West 
of Cetus, and contains 24 discernible stars. It is 
represented with open mouth, drinking the water 
in the stream of Aquarius. Fomalhant — a — a 
reddish star of the 1st magnitude, in the mouth, is 
27° Southwest from Diphda in Cetus, 20° North 
east from a Gruis, 16° nearly East from y Gnus, 
3S° Northeast from a Pavonis, 22° Northwest from 
a Phcenicis, 45° due South from Markab, in the 
West side of the Square of Pegasus, 32° South- 
east from t 3 Aquarii, 39° a little South of East from 
Capricorni, 21° Southeast from 8 Capncorni, 
40° Northwest from Aehernar — a Eridani — 60° 
Southeast from Altair, and 27° East from « Micro- 
scopii. It forms a nearly equilateral triangle with 
e 5° and ,5, 6°, distant, both of the 4th magnitude, 
P being nearly midway between Fomalhaut and a 
Gruis. West 10° from ft 16° West from a, and 5° 
above r Gruis, is i, of the 4th magnitude. 9° West 
of e is r h of the 5 th magnitude. «, e, ,, and 6, form 
an arc of stars outlining the back of the fish. _ 

119. Pegasus — The Winged Horse. This 
constellation is North of Aquarius and Piscis Oc- 
cidens, Southwest of Andromeda, and East of 
Delphinus; it contains 89 discernible stars. It is 



represented on the globe as the forward part of a 
flying horse. Algenib — the Southernmost star in 
the Eastern side of the Square -(Sec. 50) is the 
only one, of note in the constellation, not shown 
on this map. Enif-. -of the 2nd magnitude, 
in the nose, is 20° a little South of West from 
Markab, 12° above Sadalmelik, 16° above Sadal- 
sund, 2S° East from Altair, and 17° a little South 
of East from Svalocin. 

The junction of the head and neck of Pegasus 
is marked by three small stars, midway between 
Enif and the Y of Aquarius; and between these 
and Markab, 7° from the latter, in line with 
Alpheratz, is Horaan-C-of the 3rd magnitude. 
North 19° from C, and 5° West from ft is Matar 
_ r/ _of the 3rd magnitude; 6° from jj, and 5° 
from /? is m, and near it is A, both of the 4th mag- 
nitude, in the breast; * and t, both of the 4th 
magnitude, in the legs, form, with ,, a nearly equi- 
lateral triangle of S° on each side ; *, of the 4th 
magnitude, is 5° West from i. 

120. Eqttuleus. The Little Horse. The two 
stars of the 4th magnitude, 5° apart, and 8° to the 
West from Enif, forming with it a triangle, be- 
long to Equuleus— a constellation containing 10 
discernible stars; the head only is shown on the 
globe, in front of the head of Pegasus. 
° 121. The star marked £, 20° West from Matar, 
also Gienah and Albireo-the two large stars 
in the upper margin of the map — are in Cygnus. 
The course of the Milky Way is shown in the 
upper right corner. The Eastern stream includes 
Aquila (Sec. 114), and runs Northeast towards 
Cygnus. 






MAP NO. XI. 



122. This map is projected with the Equinoc- 
tial as a base line, instead of the Ecliptic. It rep- 
resents that portion of the heavens situated be- 
tween Draco and Ophiucus et Serpens. The per- 
pendicular through the center of the map is a por- 
tion of the 16 hour circle of Right Ascension ; it 
is on the meridian 2 hours before the head of 
Draco (Sec. 44), and 16 hours after, or 8 hours 
before, the Vernal Equinox. The map contains the 
handle of the Dipper and head of Draco, in com- 
mon with Map No. I., Cor Caroli and the lower 
part of Bootes, in common with Map No. VII., 
and the heads of Ophiucus and Serpens, in com- 
mon with Map No. VIII. 

123. Bootes. The Bear Driver. This con- 
stellation is represented on the globe as a man 
holding in his hand a leash, directing two dogs — 
Asterion and Chara — which are hunting the Bears 
round the Pole. It contains 54 discernible stars. 
The principal star is Arcturus — a — a reddish 
yellow star of the 1st magnitude, situated (Sec. 90) 
33° Northeast from Arista, 26° Southeast from Cor 
Caroli, 31° nearly South from Alkaid, 26° North- 
west from Unukulhay, 49° West of Rasalague, 
and 54° Southwest from Etanin. East from Arc- 
turus 8°, is ?, of the 3rd magnitude, in the left 
knee; 6° below c is C, of the 3rd magnitude, 
which is also 8° Southeast from a, these three 
forming an isosceles triangle ; tt and o, of the 3rd 
magnitude, are nearly equidistant from ? and £, a 
little nearer a, and on the line from a to Unukulhay. 

West 6° from a, nearly on a line with f , is -q — 
Muphrid — of the 3rd magnitude ; 10° Northeast 
from a is Izar — e — and 9° farther in the same 



line is Alkaturgos — 8 — a golden yellow, in the left 
shoulder;, e is 9° above f, and 12° farther is Segi- 
nus — y — a silver white star in the right shoulder ; 
s, 8 and y are all of the 3rd magnitude ; a, y, 8 
and ?, form a four sided figure, with e at the inter- 
section of the two diagonals ; and /?, of the 4th 
magnitude, is 4 a above e, in line between a and y. 
Nekkar — /? — a golden yellow star of the 3rd 
magnitude in the head, is 8° above <J, 6° north of 
east from y,. and 24° above a. From /S, 10° 
towards Alkaid, is X, of the 4th magnitude, and 5° 
north of A, and about as far from Alkaid, is (, of 
the 4th magnitude ; i forms a small right angled 
triangle with 0, of the 4th, and %■> °f tae 5t h mag- 
nitudes, in the hand of Bootes. 

121. Corona Borealis — The Northern Crown. 
This constellation is situated east of Bootes, and 
contains 21 discernible stars. Southeast 8° from 
Alkaturgos, towards the head of Serpens, is 
Alphecca — a — a brilliant white star of the 2nd 
magnitude, also 21° North from Unukulhay, and 
20° Northeast from Arcturus — the three forming 
a prominent triangle of nearly equal sides. From 
a, 3° towards Alkaturgos, is j3, of the 4th magni- 
tude. These two form a semi-circle with £, d, and 
0. The other stars in this constellation are small. 

125. Hercules — The Sampson of Greece. 
This constellation is East of Bootes, North of 
Ophiucus, and South of Draco, contains 113 dis- 
cernible stars, and is represented on the globe as a 
man in an inverted position, kneeling, holding a 
club in one hand, and the three-headed Cerberus 
in the other. The principal star is Korneforos — 
^ — a pale yellow star of the 2nd magnitude in the 



40 



ASTKONOMY. 



West shoulder, situated 32° East from Arcturus, 
35° Southwest.from Etanin, and 14° Southeast by 
East from Alphecca, in line with Rasalague. 
Southeast from /?, 13°, is Ras Algethi — a — an 
orange colored star of the 3rd magnitude in the 
head, nearly on a line towards Rasalague, and 5° 
from that star. Southwest 3° from /?, towards 
Unukulhay, is y — a silver white star of the 3rd 
magnitude ; 12° on the other side of /?, in the same 
line, is e, of the third magnitude, 7° farther is -, 
of the 3rd, and 11° still farther, in the same line, 
is t, of the 4th magnitude, only 6° South of Etanin. 
These seven stars form a slightly curved line of 
54° in length from Etanin to Unukulhay. [1 and 
y, with /, and with y and ,3 Serpentis, form an- 
other curved line of Stars. 

East 2° from - is p, and 6° farther is 0, both of 
the 4th magnitude, these marking the position of 
the Eastern thigh, and forming a triangle with t, 
of the 4th magnitude, in the foot. North 11° from 
a, Northeast 12° from /?, and 7° below s, is 3 — a 
greenish tinted star, of the 4th magnitude. A line 
from S, through e, produced 9° farther, will nearly 
touch t], of the 3rd magnitude, also <x, 4° farther, 
and r, 5° still farther — the last three marking the 
position of the Western thigh. A line from ,3, 
through d, will pass /j., £, and o — three equidis- 
tant stars, of the 4tn magnitude, in the Eastern 
arm ; 7° South of these are three stars of the 5th 



magnitude in the heads of Cerberus, 20° North 
of the head of Taurus Poniatowski. 

126. Lyka — The Harp. This is a small con- 
stellation, containing 21 discernible stars, lying 
East of Hercules, and North of the head of Draco. 
A little East of South 15° from Etanin, 30° Nbrth- 
east from Rasalague, 60° a little North of East 
from Arcturus, 32° Northeast from Korneforos, 35° 
a little West of North from Altair, and 40° a little 
North of East from Alphecca, is Vega — a — a 
sapphire colored star of the 1st magnitude ; 6° 
farther from Etanin is Sheliak — ,3 — a white star 
of the 3rd magnitude, and 2° Southeast from /3 is 
Sulaphat — y — a bright yellow star of the 3rd 
magnitude. 

The stars marked 8, 6 and z, in the upper left 
hand corner of the map, South of the first fold of 
Draco, belong to Cygnus. The Solstitial Colure, 
coincident with the 18 hour Circle, is represented as 
a curved line on the map. R passes near Grumium 
and Etanin, in the head of Draco (Sec. 44), West 
of Vega, through the heads of Cerberus, touches 
No. 72 Ophiuci, cuts the head of Taurus Ponia- 
towski, and intersects the Ecliptic in the first point 
of Y3, West 1|° from /x Sagittarii (Sec. 108). 
The star No. 72 Ophiuci, in the Southeast corner 
of the map, lies in the Milky Way, which runs 
East of Cerberus and Lyra, from the left shoulder 
of Ophiucus. 



Define and explain (the figures refer to the 

122. Map No. XI. ; projection ; connections. 123. Bootes ; Arcturus ; isosceles triangle ; Muphrid ; Alkaturgos ; 
Izar ; Nekkar. 124. Corona Borealis ; Alphecca. 125. Hercules ; Ras Algethi ; Etanin to Unukulhay ; Eastern arm ; 
Cerberus. 126. Lyra; Vega; Sheliak; Sulaphat; Cygnus; Solstitial Colure ; Milky Way. 



MAP NO. XII. 



127. This map represents a portion of the 
heavens extending from the parallel of the Winter 
Solstice — 23^° of South Declination — to a few 
degrees past the South Pole; the perpendicular 
line is the circle of 8 hours of Right Ascension. 
The map includes the Southern portion of Canis 
Major, in common with Map No. V., the whole of 
the constellation Argo, and contiguous stars, many 
of which have been previously noted. 

128. Argo — The ship in which Jason and his 
companions are said to have sailed in quest of the 
golden fleece of Aries. This constellation covers 
a large portion of the heavens lying Southeast of 
Canis Major, but the greater number of its stars 
are always below the horizon of the Northern 
States. It contains 64 discernible stars, two of 
which — p and c-, both of the third magnitude — in 
the beak of the prow, are shown on Map No. V. 
Tureis — p — is 21° Southeast from Sirius, and 25° 
Southwest from Alphard ; ? is 4° West from p. 
South 37° from Sirius, 21° Southeast by South from 
Phact, and 30° East from Achernar, is Canopus — 
a — of the first magnitude, under the front of the 
keel. 

Southeast 29° from Sirius, in line with Betel- 
gueuse, 16° South from Tureis, and 21° Northeast 
from Canopus, is Naos — C — of the 2nd magni- 
tude, in the forward deck. Southeast by South 
25° from a, is /?, of the 1st magnitude, under the 
stern, -with 9h. 12m. of Right Ascension, and 69° 
South Declination, or 159° of North Polar Distance. 
Above /?, 12° towards Aludra, and 18° Southeast 
by East from a, is e, of the 2nd magnitude ; East 
7° from e, and 25° from a, is c, of the 2nd magni- 



tude ; East 11° from i is y, of the 2nd magnitude ; 
0, of the 3rd magnitude, is 5° South from y, and 
ix, of the 3rd, is 11° North from -q. These three — 
[i, 7], and 0— form a line North and South, with 
lOh. 40m. of Right Ascension, and mark the stern, 
or Eastern, line of the ship ; on the globe they are 
generally represented as in the body of a tree 
called Robuk Caeoli, or Charles' Oak, but they 
are catalogued as in Argo, and the tree is not 
placed on these maps. North 15° from /3, and 4° 
above i, is x, of the 3rd magnitude ; these three 
forming another line running North and South, 
with a Right Ascension of about 9h. 15m. South- 
east 1° and 12° from t, are u and w, of the 4th 
magnitude, the two latter marking the shortest 
diagonal of a perfect diamond with y? and — the 
latter being 10^° apart; 7° above e is /, of the 4th 
magnitude, and 6° above t is 8, of the 3rd magni- 
tude ; these four form another diamond group of 
almost exactly the same size and shape as the for- 
mer, and about 1° Northwest from it; ^ is 14° 
East from a. 

Sirius forms a line with y, of the 2nd, 8, c, and 
0, the distances being : from Sirius to y, 36° ; y to 
8, 9° ; 8 to t, 6° ; and ( to 0, 11° ; 0, 8, and p., form 
a nearly equilateral triangle, averaging 18° on each 
side ; e and c, in the South side of the Western 
diamond, form a trapezium with /3 and o, farther 
South, almost identical in size and shape with the 
bowl of the Great Dipper ; the Western diamond, 
with x, 4° North from t, forms a figure of five stars, 
similar to the group in the head of Draco, x-> at 
the acute angle, being in the Western end ; North 
16° from f, is X, of the 3rd magnitude, with a little 



42 



AST EONOMT. 



more than 9 hours of Right Ascension. The 
smaller stars in the constellation, including those 
in the sails, sometimes counted separately from 
Argo, may be easily located from the map. 

129. Southeast by South 45° from Canopus, 
20° a little North of East from /?, East 11° from 0, 
and 12£° from ij, is a Crucis — of the 1st magni- 
tude — the most Southerly star in the Southern 
Cross, situated just East of the hinder legs of the 
Centaur (Sec. 95) ; d Crucis, of the 3rd magnitude, 
and a, form a parallelogram with and y Argus, 
the longest side of which is parallel with the Equi- 
noctial. East 30° from ,3 Argus, in line with Can- 
opus, is Agena — /S — and 5° East of /2 is a 2 — 
both of the 1st magnitude, and located in the front 
feet of the Centaur, whence a Centauri is some- 
times called " Ungula " — the hoof. 

South, 5° from a Crucis, are a and j3 Muscae, of 
the 4th magnitude, forming with y and <J, 5° farther 
South, a small trapezium which maiks the loca- 
tion of the Southern Fly (Sec. 57). Southeast 9° 
from Ungula, and just outside the margin of the 
map, is y Triangulis Australis, of the 3rd magni- 
tude (Sec. 101). a Circini, of the 4th magnitude, 
between y Triangulis and Ungula, is the only star 
of note in a small constellation known as " The 
Compasses." Below Canopus 11°, and 22° West 
from ,<? Argus, is /? Doradus (Sec. 73), of the 4th 
magnitude. East of South, 10° from Canopus, is a 
Pictoris, of the 4th magnitude, the only notable 
star in The Painter's Easel. West 24° from [i 
Argus, in line with Achernar, is y Hydri, of the 3rd 
magnitude (Sec. 71) ; a Hydri is 16° farther in 
the same line; 13° West from y Hydri, is ,2, of the 
3rd magnitude ; y and /3 form an isosceles triangle 
with Achernar. 

130. The region near the South Pole is 



singularly barren in stars visible with the naked 
eye ; the star of the 5th magnitude, South of ,3 
Hydri, belongs to the constellation Octans — the 
Octant; it is the only star of greater magnitude 
than the 6th, near the Pole; and there are none 
exceeding it in apparent size, within a large area. 
The seemingly vacant space is filled up on the 
globe by several figures, as : Mons Mensae (The 
Table Mountain), between Dorado and the Pole t 
Piscis Volans (The Flying Fish), just West of ,3 
Argus; and the Chameleon, South of Musca and 
the stern of Argo. The nearest important stars, 
near the downward continuation of the perpen- 
dicular line on the map, are 8, /J, and y Pavonis 
(Sec. 112), on the Antarctic circle; the middle 
star — ,3 — has 20-J hours of Right Ascension. 
The course of the Milky Way is very strongly 
marked in the region represented on this map; it 
runs from Canis Major, through the prow of the 
ship, and along the deck to the feet of the Centaur, 
which it includes, crossing several successive hour 
circles at nearly the same distance from the Pole ; 
then turns Northward. The feet of the Centaur 
mark the Southern bend of the luminous band; 
it recedes from the South Pole on e ich side of 
Centaurus. From the Cross Westward, it rnns 
through Argo, Monoceros, the feet of Gemini, the 
East part of Orion, Auriga, Perseus, Cassiopeia, 
and to the head of Cepheus. Here it divides, pass- 
ing through Cygnus in two streams, which meet in 
the tail of Scorpio, and flow unitedly through Ara 
to Centaurus. One stream from Cygnus passes 
through Delphinus, Aquila, the feet of Antinous, 
Shield of Sobieski and the bow of Sagittarius to 
the tail of Scorpio ; the other stream from Cygnus, 
through Anser (Sec. 132), Taurus Poniatowski, 
the side of Ophiucus, and the tail of Scorpio. 



Define and explain (the figures refer to the sections) : 

127. Map No. XII ; connections. 128. Argo, Tureis ; Canopus ; Naos ; stern line ; Robur Caroli ; two diamond 
groups; Equilateral triangle. 129. Crux; Agena; Ungula; Musca; Triangulum Australis; Circinus; Doradus; 
Pictoris ; Hydrus. 130. Octans ; bare of stars ; Course of the Milky Way. 




■•^^■^U^^Hb 



V* -j^ 



MAP NO. XIII. 



131. This map is divided into two portions, 
the upper section showing a part of the Northern, 
the lower section a part of the Southern Hemis- 
phere. 

132. Cygnus. The Swan. This constellation, 
represented in the upper part of the Map, is situ- 
ated South of Cepheus, Southeast of the head of 
Draco, North of East from Lyra, and North- 
west of Pegasus ; it contains 81 discernible stars. 
Deneb — a — a brilliant white star of the 1st 
magnitude, with 20h 38m of Right Ascension, is 
28° a little South of East from Etanin, 24° a 
little North of East from Vega, 18° a little West 
of South from Alderamin, 38° a little East of 
North from Altair, and 33° Northwest from Scheat 
Pegasi, in direct line with Algenib at the opposite 
corner of the Great Square. Its Declination is 
44° 50, North Polar Distance 45° 10; it is hence 
nearly in the Zenith of the Northern States when 
on the Meridian. 

Southwest 6° from a is Sadr — j — a yellow col- 
ored star of the 3rd magnitude, and 16° farther, 
and the same distance from Vega, is Albireo — ,3 — 
a topaz yellow in the beak, and of the 3rd magni- 
tude ; <p, of the 4th magnitude, is 2° from /S towards 
a. y, y, and j3, form an easily traced line in the 
heavens, which is crossed at y by two stars of the 
3rd magnitude, each 8° from y — e, Gienah, on the 
Southeast, and 3, on the Northwest, in line 
towards Etanin. Nearly in the same line, 7° 
Southeast from Gienah, is C, of the 3rd magni- 
tude, in the Eastern wing. North 6° and a little 
West from 3, is 0, of the 4th magnitude, and 5° 



Northwest from is x, of the 4th magnitude, near 
the first fold of Draco. 

Prom Deneb, 6° towards 0, and forming a trape- 
zium with a, y, and 3, is o a , of the 4th magnitude, 
Southeast 5° from a is v, of the 4th magnitude ; and 
3° farther South, in the same line, and nearly East 
from Vega, is a star marked No. 61, in reality two 
stars of the 6th magnitude, revolving round each 
other, and forming the first discovered system of 
two sun-stars revolving about a common center. 
The stars marked a, y, and Z y near the North mar- 
gin of the map, are in Cepheus. 

Near the Eastern margin, with 40° of North 
Polar Distance, is a Lacertae, of the 4th magni- 
tude, the only star of note in the constellation 
called The Lizard ; - 2 Pegasi, in the Southeast 
corner, is in the Northern hoof of Pegasus. Im- 
mediately South of Cygnus is a space between it 
and Aquila and Delphinus, which has been mapped 
out as belonging to Vulpecula et Anser (the Fox 
and Goose), and Sagitta (The Arrow). It con- 
tains no noteworthy stars, and the constellations 
are not, therefore, placed on these maps. Sagitta 
is an ancient constellation — the other a modern one. 

The Milky Way runs through the section of 
the heavens represented in the upper half of this 
map. The Western stream from Ophiucus runs 
Northeast across the map, including the head and 
neck of Cygnus. The Eastern stream from Aquila 
takes the East wing of Cygnus in its course, from 
Gienah nearly to C, and the two streams run 
parallel across the body, uniting in the head of 
Cepheus. 



44 



ASTRONOMY. 



133. Centaukus et Crux — The Centaur and 
the Cross. This constellation is represented in the 
lower section of Map No. XIII. , the circle of 13 
hours of Right Ascension being the central line. 
The Centaur is represented on the globe as a 
monster, half man and half horse, with-shield and 
spear, attacking the Wolf in his front. This con- 
stellation contains 35 discernible stars, including 5 
in the Cross, which is often spoken of@as a sepa- 
rate constellation. The Centaur lies South of the 
tail of Hydra, Southwest of Libra and Scorpio, 
East of Argo, West of Ara, and East of the 12 
hour circle; x Centauri and ft Lupi, both of the 
3rd magnitude, and 1° apart, lying 24° Southwest 
from Antares (Sec. 99) are 13° East from n and v, 
both of the 3rd to the 4th magnitude, and are 4° 
East from tj, of the 3rd magnitude; and t, of the 
3rd magnitude, 10° apart, in the shoulders, are on an 
East and West line, 6° and 7° above v, and form 
with it an inverted triangle, the base of which is 
parallel with the Equinoctial ; and « form a dia- 
mond figure with 1} and v, and the two latter form 
a lower quadrilateral with f, of the 3rd magnitude, 
6° South from v, and a Lupi 6° below 5?. These, 
with k, of the 4th magnitude, in the head, and a 
few smaller stare in the shield, are all of the Cen- 
taur, visible North of the Gulf of Mexico. The 
most prominent stars in the constellation never 
rise above the horizon of the United States. 

East 11° from d Argus, is a Crucis, of the 1st 
magnitude, and 6° North from a, is y, of the 2nd 
magnitude, these two forming the upright portion 
of the Cross, situated a little East of the 12 hour 
circle, and pointing to the South Pole, which is 
27£° from a ; 4° apart, and nearly perpendicular 
to these, are /?, of the 2nd magnitude, and 3, of the 
3rd, the latter being nearly on the 12 hour circle, 



and with 3 Centauri, of the 3rd magnitude, 8° 
Northward, lying on the Equinoctial Colure, with 
a Corvi, 3 Ursa? Majoris, j3 Cassiopeia?, a Andro- 
mcdse, y Pegasi, and /3 Hydri, the latter being on 
the other side of the South Pole from the Cross ; 
3 is 18° West from C ; and 6° East from 3 towards 
C, is y, of the 3rd magnitude ; e, of the 3rd mag- 
nitude, is nearly half way between C and ,3 Crucis, 
a Crucis is 11° East from Argus, and 12° farther 
East is Agena — ,3 Centauri — of the 1st mag- 
nitude, in the second fore foot; 5° farther East, 
and 33° from ,3 Argus,_ 9° West from /? Trianguli, 
and 22° West from ,3 Arse (Sec. 100), is a* Cen- 
tauri, of the 1st magnitude — Ungula — close to 
this is a 1 , of the 4th magnitude, both in the for- 
ward hoof of Centaurus. 

13 4. Lupus — The Wolf. This constellation 
lies East of Centaurus, the head towards the 
North, and nearly touching the body of Scorpio ; 
it contains 24 discernible stars. Southwest 6° from 
/?, of the 2nd magnitude (Sec. 99), just South of z 
Centauri, is a, of the 3rd magnitude, forming 
an isosceles triangle with /3 Lupi and i\ Centauri. 
Southeast 7° from a is C, of the 4th magnitude; 
East from x Centauri, and 12° above C, is y, 
of the 3rd magnitude. 13° North of x Centauri, 
towards Zubenelg is 3, of the 4th magnitude, in 
the fore paw ; Northeast from y, and 2^° apart, are 
and 17, both of the 4th magnitude, in the face. 
These are all the stars worthy of note in the con- 
stellation. 

' The Milky Way skirts the Southern limit of 
the lower section of the map, its Northern edge 
passing through the middle of Crux, and just out- 
side of the fore feet of the Centaur. It con- 
nects with Argo West of the Centaur, and with 
Ara to the East. 



Define 1 



1 explain (the figures refer to the sections) : 



131. Map No. XIII. 133. Cygnus; location; Deneb ; Sadr ; Albireo ; Gienah ; the Cross; remarkable star; the 
Lizard; Vulpecula ct Anscr ; S.-i-jitta ; .Milky Way. 133. Centaurus et Crux ; Lupus; Shoulder hue; shield; The 
Southern Cross ; Equinoctial Colure ; Ungula. 134. Lupus. 



TABLE OF FIXED STARS. 



135. The following table contains the places of 
the principal fixed stars, including all of the 1st, 
2nd, and 3rd magnitudes, those of the 4th within 
the Zodiacal constellations, and in other groups in 
which there is no more prominent star ; also a few 
of the 5th magnitude, and the Beehive nebula. 
The places are given in Right Ascension, North 
Polar Distance (Sec. 20), Longitude, and Latitude, 
for the beginning of the year 1875. The annual 
variation in Right Ascension and North Polar 
Distance, is also given for each star ; marked + 
when the correction should be added for future 
years, and — when the correction should be 



subtracted from the tabular quantity for each 
subsequent year. For years previous to 1875, 
subtract where marked +, and add where the 
minus sign is given. Astronomers prefer the 
notation in North Polar Distance to that of Decli- 
nation, in the tables, as it preserves a greater 
degree of uniformity in the signs (plus and minus) 
of the variation. The annual variation in Longi- 
tude of all the stars, is + 50^." The Latitudes 
do not vary. 

The Longitudes and Latitudes are given to the 
nearest -j^th of a minute of Arc. 



MAO, 


STAR. 


ET. ASCEN. 


ANN. VAK. 




1. P. D. 


ANN. VAR. 




LONG. 


LAT. 


1 


a Androm. ; Alphemtz. 


lm 16s 


+ 3.01s 


61 c 


35' 58' 


— 19.9" 


T 


12 c 


34.1' 


N25 c 


41.0' 


2-3 


ft Cassiopeise ; Chaph. 


2m 31s 


3.16 


31° 


32' 23" 


19.9 


8 


3° 


21.2' 


N51 c 


12.6 


2 


y Pegasi ; Algenib. 


6m 48s 


3.08 


75 c 


30' 41" 


20.0 


cp 


7° 


24.9' 


N 12 c 


36.8' 


3 


ft Hydri. 


19m 09s 


3.27 


167 c 


57' 38" 


20.3 


Y3 


29° 


5.3' 


S 64 c 


41.4' 


2 


a Phoenicis. 


20m 06s 


2.98 


132 c 


58' 59" 


19.7 


X 


13° 


44.1' 


S 40 c 


36.7' 


3 


8 Andromedse. 


32m 39s 


3.19 


59° 


49' 25" 


19.8 


cp 


20° 


4.3' 


N 24 c 


20.6' 


3 


a Cassiopeia? ; Schedir. 


33m 26s 


3.37 


34 c 


8' 54" 


19.8 


8 


6° 


3.1' 


N 46° 


36.8' 


2-3 


ft Ceti; Diphda. 


37m 19s 


3.02 


108 c 


40' 23" 


19.9 


cp 


0° 


49.3' 


S 20° 


47.0' 


5 


3 Piscium. 


42m 12s 


3.11 


83 c 


5' 43" 


19.7 


cp 


12° 


24.0' 


N 2° 


10.4' 


3 


y Cassiopeiae. 


49m lis 


3.56 


29 c 


57' 37" 


19.6 


8 


12° 


12.0' 


N48° 


48.1' 


4 


e Piscium. 


56m 28s 


3.11 


82° 


47' 0" 


19.5 


cp 


15° 


47.0' 


N 1° 


5.1' 


3-1 


ft Phoenicis. 


I 0m 30s 


2.69 


137 c 


23' 17" 


19.4 


X 


18° 


40.6' 


S 48° 


12.0' 


2 


ft Andromeda? ; Mirach. 


2m 44s 


3.34 


55° 


2' 31" 


19.3 


cp 


28° 


39.8' 


N25° 


56.1' 


2 


a Urs. Mill. ; Alnicrahal, 


12m 55s 


20.40 


1° 


21' 25" 


19.1 


n 


26° 


49.2' 


N 66° 


5.1' 


3 


d Cassiopeias- Ruchbah. 


17m 39s 


3.87 


30° 


24' 54" 


18.9 


8 


16° 


11.0' 


N46° 


23.8' 


3 


Ceti. 


17m 49s 


3 00 


98° 


49' 43" 


18.7 


cp 


14° 


29.0' 


S 15° 


46.0' 


3 


Y Phoenicia. 


22m 57s 


2.63 


133° 


57' 29" 


18.6 


X 


20° 


23.3' 


S 47° 


34.8' 


4-5 


p. Piscium. 


23m 38s 


3.14 


84° 


30' 8" 


18.6 


cp 


21° 


22.7' 


S 3° 


4.0' 


4 


f] Piscium. 


24m 48s 


3.20 


75° 


17' 56" 


18.8 


cp 


25° 


4.3' 


N 5° 


22.1' 


3-4 


51 Andromedse. 


I 30m 20s 


+ 3.65 


42° 


0' 22" 


— 18.4 


8 


10° 


42.2' 


N 35° 


24.3' 



46 



ASTRONOMY. 



M\0 


STAB. 


RT. ASCEN. 


Aim. VAR. 


N. P. D. 


ANN. VAR. 




LONG. 


LAT. 


1 


a Eridani ; AcJiernar. 


I 33m 3s 


+ 2.24s 


147' 


3 52' 19" 


— 18.4s 


X. 


13 c 


' 31.9' 


S 59 c 


' 22.3' 


3 


Z Ceti ; Baton Kaitos. 


45m 17s 


2.96 


100 1 


3 57' lb" 


17.9 


cp 


20 c 


' 11.9' 


S 20 ( 


' 20.5' 


3 


e Cassiopeia?. 


45m 25s 


4.24 


26' 


5 56' 47" 


18.0 


8 


23 c 


1 1.7' 


N47< 


' 32.0' 


3-4 


a Trianguli. 


45 m 58s 


3.40 


61' 


D 1' 50" 


17.8 




5 C 


' 7.4' 


N16 C 


' 47.9' 


3 


/? Arietis ; Sheratan. 


47m 44s 


3.30 


69 c 


1 48' 13" 


17.8 


8 


2 C 


' 13.5' 


N 8 C 


' 28.9' 


3 


a Hydri. 


54m 50s 


1.89 


152 c 


' 10' 44" 


17.6 


X 


10 c 


' 19.1' 


S 64< 


' 13.8' 


3-4 


a Piscium ; I?Z Rischa 


55m 35s 


3.10 


87 c 


: 50' 24" 


17.6 


cp 


27 c 


' 37.8' 


S 9 C 


1 4.2' 


3 


y Androni. ; Almaach. 


50m 14s 


3.65 


48 c 


' 16' 15" 


17.6 


a 


12 c 


1 29.1' 


1ST27' 


' 47.7' 


2 


a Arietis ; Hamal. 


II 0m 8s 


3.36 


67 c 


' 7' 45" 


17.3 


8 


5 C 


' 54.9' 


N 9 C 


' 57.7' 


Var 


. o Ceti ; Mir a. 


13m 2s 


3.02 


93 c 


' 32' 47" 


16.6 


T 


29 c 


1 46.6' 


S 15' 


' 56.°' 


4 


35 Arietis. 


36m 7s 


3.50 


62 c 


' 49' 30" 


15.7 


8 


15 c 


1 11.5' 


N 11' 


' 18.0' 


3 


p Ceti. 


36m 49s 


3.10 


87 c 


' 17' 32" 


15.4 




7 C 


' 41.6' 


S 12 c 


' 0.3' 


4 


fi Arietis. 


38m lis 


3.23 


80 c 


24' 53" 


15.5 




10 c 


1 19.0' 


S 4 C 


' 17.6' 


5 


7: Arietis. 


42m 19s 


3.33 


73 c 


' 3' 22" 


15.3 




13 c 


' 22.4' 


N r 


' 48.7' 


3 


41 Arietis. 


42m 38s 


3.51 


63 c 


1 15' 2]" 


15.2 




16 c 


' 27.6' 


N10 C 


' 26.3' 


3 


tj Eridani ; Azha. 


50m 19s 


2.93 


99 c 


' 23' 47" 


14.6 




6 C 


1 59.9' 


S 24 c 


' 33.0' 


2-3 


a Ceti ; Menkar. 


55m 45s 


3.13 


86 c 


24' 7" 


14.4 




12° 


34.4' 


S 12 c 


' 35.8' 


3-4 


y Persei. 


55m 45s 


4.31 


36° 


59' 6" 


14.4 




28° 


16.9' 


N34 c 


30.8' 


2-3 


/3 Persei; Algol. 


III 0m 2s 


3.87 


49° 


31' 36" 


14.3 




24° 


25.6' 


N 22 c 


' 24.8' 


4 


S Arietis. 


4m 29s 


3.42 


70° 


44' 50" 


14.0 


8 


19° 


6.1' 


N l c 


1 48.6' 


2-3 


a Persei; Mirfah. 


15m 24s 


4.24 


40 c 


35' 9" 


13.1 


n 


0° 


20.3' 


N 30 c 


1 6.6' 


4-5 


10 Tauri. 


30m 30s 


3.06 


89° 


59' 47" 


11.7 


8 


20° 


13.2' 


S 18 c 


26.1' 


3 


d Persei. 


34m 2s 


4.24 


42° 


36' 51" 


11.9 


n 


3° 


3.5' 


N 27 c 


1 17.1' 


3-4 


3 Eridani. 


37m 16s 


2.87 


100° 


11' 15" 


12.5 


8 


19° 


6.4' 


S 28 c 


1 43.4' 


5 


19 Tauri. 


37m 46s 


3.56 


65° 


55' 34" 


11.7 




27° 


49.2' 


N 4° 


30.2' 


3 


rj Tauri ; Alcyone. 


40m 3s 


3.55 


66° 


15' 58" 


11.6 


8 


28° 


14.9' 


N 4° 


2.2' 


3-4 


C Persei. 


46m 17s 


+ 3.75 


58° 


29' 22" 


11.0 


n 


1° 


22.8' 


N ll c 


19.0' 


3 


r Hydri. 


49m 14s 


— 1.01 


164° 


37' 21" 


10.9 


w 


4° 


41.0' 


S 76° 


21.3' 


2-3 


Y Eridani ; Zaurak. 


52m 12s 


+ 2.80 


103° 


51' 55" 


10.6 


8 


22° 


7.0' 


S 33° 


12.8' 


4 


X Tauri. 


53m 45s 


3.31 


77° 


51' 51" 


10.6 


8 


28° 


53.3' 


S 7° 


58.5' 


3-4 


Y Tauri. 


IV 12m 41s 


3.41 


74° 


40' 34" 


9.0 


n 


4° 


4.4' 


S 5° 


44.7' 


3-4 


a Reticuli. 


12m 49s 


0.74 


152° 


47' 18" 


9.0 


cp 


5° 


39.6' 


S 78° 


2.8' 


4 


^i Tauri. 


15m 44s 


3.45 


72° 


45' 9" 


8.8 


n 


5° 


7.3' 


S 3° 


59.0' 


3-4 


e Tauri. 


21m 19s 


3.49 


71° 


5' 55" 


8.4 


n 


6° 


42.9' 


S 2° 


34.9' 


1 


a Tauri; Aldeoaran. 


28m 45s 


3.44 


73° 


44' 37" 


7.6 


n 


8° 


4.5' 


S 5° 


28.6' 


3-4 


u ' Eridani ; Theemin. 


30m 42s 


2.33 


120° 


49' 12" 


7.7 


8 


28° 


8.1' 


S 51° 


50.1' 


3 


a Doradus. 


31m 18s 


1.29 


145° 


18' 15" 


7.6 


8 


6° 


2.0' 


S 74° 


35.6' 


4 


a Camelopardi. 


41m 12s 


5.92 


23° 


54' 22" 


6.7 


n 


19° 


10.1' 


N43° 


22.6' 


4-5 


£ Tauri. 


55m 37s 


3.58 


68° 


35' 26" 


5.5 




15° 


2.4' 


S 1° 


12.9' 


3 


/3 Eridani ; Cursa. 


V Ira 42s 


2.95 


95° 


14' 58" 


5.1 




13° 


36.0' 


S 27° 


53.6' 


5 


15 Orionis. 


2m 33s 


3.43 


74° 


33' 50" 


5.0 




16° 


3.0' 


S 7° 


19.7' 


1 


a Aurigae; Capella. 


7m 27s 


4.42 


44° 


7' 54" 


4.1 




20° 


6.8' 


N 22° 


51.8' 


1 


,<? Orionis; Rigel. 


8m 32s 


2.88 


98° 


20' 51" 


4.6 




15° 


5.0' 


S 31° 


8.4' 


2 


[1 Tauri; El Nath. 


18m 24s 


3.79 


61° 


30' 2" 


3.4 




20° 


50.0' 


N 5° 


22.4' 


2 


Y Orionis ; Bellatrix. 


5 18m 26s 


+ 3.22 


83° 


45' 56" 


— 3.6 


n 


19° 


12,1' 


S 16° 


50.0' 



TABLE OF FIXED STABS. 47 

MAG. STX3. RT. ASCEN. ANN. TAR. N. P. D. ANN. TAR. LONG. LAT. 

2 S Orionis; Mintaka. V 25m 37s + 3.07s 90° 23' 38" — 3.0s n 20° 37.0' S 23° 34.3' 
3-4 a Leporis ; Arneb. 27m 13s 2.65 107° 54' 47" 3.0 19° 38.1' S 41° 4 .6' 
2-3 e Orionis; Alnilam. 29m 52s 3.04 91° 17' l" 2.6 21° 43.1' S 24° 31.5' 
3-4 C Tauri. 30m lis 3.58 68° 56' 9" 2.6 23° 2.4' S 1° 45.5' 

3 C Orionis; Alnitdk. 34m 27s 3.03 92° 0' 40" 2.2 22° 56.2' S 25° 18.7' 

2 a Columbse; Phact. 35m 8s. 2.18 124° 8' 32" 2.2 20° 25. '5 S 57° 23.6' 

3 x Orionis; Saiph. 41m 50s 2.85 99° 42' 57" 1.7 24° 39.2' S 33° 5.2' 
4-5 136 Tauri. 45m 28s 3.77 62° 25' 13" 1.2 26° 46.4' IT 4° 9.8' 

3 /? Columbse. 46m 33s 2.11 125° 49' 5" 1.5 24° 40.3' S 59° 12.9' 

1 a Orionis; Betelgueuse. 48m 24s 3.25 82° 37' 6" 1.0 27° 0.5' S 16° 2.7' 

3-4 3 Aurigas. 49m 14s 4.94 35° 43' 40" 0.8 28° 10.2' N 30° 50.2' 

2 i3 Aurigaa ; Menkalinan. 50m 22s 4.40 45° 4' 5" — 0.8 n 28° 10.0' N 21° 29.4' 

4 f] Geminorum ; Tejat. VI 7m 20s 3.62 67° 27' 33" + 0.6 © 1° 41.7' S 0° 54.3' 

3 ix Geminorum. 15m 24s 3.64 67° 25' 28" 1.5 3° 33.4' S 0° 50.0' 
2-3 C Canis Majoris; Phurid. 15m 31s 2.30 120° 0' 34" 1.3 5° 38.3' S 53° 23.5' 

2-3 /J Canis Majoris ; Mirzam. 17m 12s 2.64 107° 53' 43" 1.4 5° 26.8' S 41° 16.3' 

1 a Argus; Canopus 21m lis 1.33 142° 37' 41" 1.8 13° 14.4' S 75° 50.3' 

4 v Geminorum. 21m 32s 3.57 69° 42' 39" 1.9 5° 1.8' S 2° 17.5' 
2-3 y Geminorum ; Alhena. 30m 29s 3.47 73° 29' 45" 2.7 7° 21.5' S 6° 45.6' 
3 v Argus. 33m 56s 1.83 133° 5' 10" 2.8 15° 21.3' S 66° 5.8' 

3 e Geminorum; Mebsuta. 36m 15s 3.70 64° 44' 51" 3.2 8° 11.6' IN" 2° 7.4' 

4 £ Geminorum. 38m 1 7s 3.37 76° 58' 18" 3.5 9° 28.2' S 10° 6.8' 

1 a Canis Majoris; Sirius. 39m 38s 2.65 106° 32' 43" 4.5 ® 12° 21.9' S 39° 34.2' 
4 a Pictoris. 46m 54s 0.61 151° 48' 28" 3.8 SI 22° 33.7' S 83° 3.4' 
2-3 e Canis Majoris ; Adhara. 53m 43s 2.36 118° 48' 11" 4.6 S> 19° 2.7' S 51° 22.6' 

4 C Geminornm. 56m 42s 3.57 69° 14' 54" 4.9 13° 14.8' S 2° 3.4' 

3-4 3 Canis Maj.; Wesen. VII. 3m 19s 2.44 116° 11' 45" 5.4 21° 39.7' S 48° 28.2' 

4-5 X Geminorum. 10m 55s 3.46 73° 14' 9" 6.1 17° 2.2' S 5° 39.0' 

3 d Geminorum; Wasat. 12m 40s 3.60 67° 47' 23" 6.3 16° 46.5' S 0° 11.8' 

3 it Argus. 12m 45s 2.14 126° 52' 26" 6.2 28° 35.2' S 58° 32.8' 

4 i Geminorum. 17m 58s 3.74 61° 57' 20" 6.8 17° 13.0' 1ST 5° 44.8' 

2 t] Canis Majoris ; Aludra. 19m 9s 2.37 119° 3' 39" 6.7 27° 48.3' S 50° 37.6' 

3 ,3 Canis Mm. ; Gomeisa. 20m 22s 3.26 81° 27' 37" 6.9 20° 27.1' S 13° 30.1' 
1-2 a 2 Geminorum; Castor. 26m 37s 3.85 57° 50' 22" 7.5 18° 30.1' N 10° 5.1' 

1 a Canis Min. ; Procyon. 32m 45s 3.14 84° 27' 19" 8.8 24° 3.7' S 15° 58.1' 

4 x Geminorum. 36m 54s 3.63 65° 18' 15" 8.3 21° 55.3' ]ST 3° 4.0' 

2 /3 Geminorum; Pollux. 37m 40s 3.68 61° 40' 26" 8.3 2> 21° 29.4' N 6° 40.5' 
2-3 Z Argils; Naos. 59m 12s 2.11 129° 39' 10" 10.0 Si 16° 50.1' S 58° 22.5' 
3-4 p Argus ; Tureis. VIII. 2m 13s 2.56 113° 56' 41" 10.0 Si 9° 39.7' S 43° 17.1' 
4 ^ s Cancri. 2m 55s 3.63 64° 6' 52" 10.6 £o 27° 30.3' N 0° 32.0' 

2 y Argus. 5m 40s 1.84 136° 58' 9" 10.5 Si 25° 38.4' S 64° 28.3' 

4 (t Cancri. 9m 44s 3.26 80° 25' 50" 10.7 S\ 2° 31.0' S 10° 17.9' 

2 e Arcrus. 19m 57s. 1.24 149° 6' 24" 11.3 TTTJ 21° 23.7' S 72° 39.2' 

4 d Hydras. 31m 2s 3.18 83° 51' 40" 12.2 Si 8° 33.9' S 12° 24.2' 

Neb Cancri ; Prcesepe. 8 33m 16s ■+ 3.48 69° 54' 0" + 12.5 Si 5° 33.6' N 1° 14.0' 



48 



ASTEONOMT. 



MAG. STAR. ET. ASCEN. ANN. VAR. N. P. D. ANN. TAR. 

4-5 y Cancri ; N. Asell. VIII 36m 3s + 3.49s 68° 4' 57" + 12.5s 

4-5 d Cancri ; Sou. Asellus. 37m 35s 3.42 71° 23' 15" 12.9 

3 d Argils. 41m 15s 1.65 144° 15' 5" 13.1 
3-4 t Ursa Majoris ; Talita. 50m 37s 4.11 41° 28' 10" 13.9 

4 a Cancri: Acubens. 51m 39s 3.29 77° 39' 34" 13.6 



LONG. LAT. 

a 5° 47.8' N 3° 10.7 

il 6° 58.5' N 0° 4.5 

TIE 17° 14.3' S 67° 11.8 

a 1° 3.9' N 29° 34.5' 

a 11° 53.8' S 5° 5.5' 



A Argus. IX 


3m 23s 


2.20 


132° 


55' 46" 


14.4 


m. 


9° 


27.9' 


S 55° 


53.3' 


Hydras. 


7m 52s 


3.13 


87° 


9' 32" 


14.9 


a 


18° 


32.3' 


S 13 c 


3.1' 


/3 Argus. 


11m 49s 


0.68 


159° 


12' 11" 


14.8 


m 


0° 


17.4' 


S 72° 


13.1' 


a Lyncis; (The Lynx) 


13m 26s 


3.68 


55° 


4' 50" 


14.9 


a 


10° 


6.0' 


N 17° 


57.2' 


t Argus. 


13m 45s 


1.60 


148 c 


45' 2" 


14.9 


=== 


3 C 


37.6' 


S 67° 


4.7' 


x Argus. 


18m 15s 


1.85 


144 c 


28' 42" 


15.3 


m 


27 c 


9.4' 


S 63 c 


57.5' 


a Hydra? ; Alphard. 


21m 27s 


2.95 


98° 


7' 4" 


15.3 


a 


25 c 


32.5' 


S 22 c 


23.5' 


Ursae Majoris. 


24m 29s 


4.03 


37 c 


45' 16" 


16.1 




5 C 


36.4' 


N34 c 


53.8' 


o Leonis. 


34m 29s 


3.23 


79 c 


32' 24" 


16.1 




22 c 


30.5' 


S 3 C 


45.8' 


e Leonis. 


38m 45s 


3.42 


65° 


39' 4" 


16.3 


a 


17 c 


55.2' 


N 9 C 


24.6' 


o Argus 


43m 59s 


1.50 


154 c 


29' 33" 


16.6 


^ 


21 c 


11.1' 


S 67 c 


29.6' 


H Leonis ; Rased Asad. 


45m 39s 


3.63 


63° 


24' 19" 


16.7 


a 


19 c 


41.4' 


N12 C 


20.8' 


■q Leonis. X 


Orn 31s 


3.28 


72° 


37' 43" 


17.3 




26 c 


9.5' 


N 4 C 


51.4' 


a Leonis (Cor) ; Requlus. 


Ira 43s 


3.21 


77° 


25' 22" 


17.4 




28° 


5.2' 


N C 


27.6' 


C Leonis ; Aldhafara. 


9m 44s 


3.35 


65° 


57' 36" 


17.7 




25° 


49.0' 


Nll c 


51.3' 


y Leonis ; Algeiba. 


13m 5s 


3.32 


69° 


31' 37" 


18.0 




27 G 


51.2' 


N 8 C 


48.6' 


H Urs. Maj. ; El Pheclcra. 


14m 53s 


3.60 


47° 


52' 21" 


17.9 




19° 


29.1' 


N 28 c 


59.3' 


fi Leonis Minoris. 


20m 39s 


3.50 


52° 39' 10" 


18.3 


a 


22 c 


47.4' 


N25° 


3.4' 


6 Argus. 


38m 30s 


2.12 


153° 


44' 23" 


18.8 


^ 


27 c 


28.5' 


S 62 c 


7.8' 


7] Argus. 


40m 13s 


2.30 


149 c 


1' 38" 


18.7 




20 c 


25.8' 


S 58 c 


54.9' 


fi Argus. 


4«lm 24s 


2.56 


138 c 


45' 34" 


19.9 


^ 


8 C 


47.4' 


S 51° 


5.2' 


a Crateris ; Alhes. 


53m 31s 


2.92 


107 c 


37' 58" 


19.0 


TIE 


21 c 


1.8' 


S 23° 


6.4' 


(3 Urs. Maj . ; Merah. 


54m 17s 


3.67 


32 c 


56' 53" 


19.2 


a 


17 C 


40.4' 


N45° 


7.1' 


a Urs. Maj. ; Dubhe. 


56m 0s 


3.76 


27 c 


34' 29" 


19.3 


a 


13° 


26.4' 


N 49° 


36.5' 


jS Crateris. X] 


5m 31s 


2.95 


112° 


8' 36" 


19.6 


HE 


26 c 


49.0' 


S 25° 


38.4' 


d Leonis ; Zozma. 


7m 28s 


3.21 


68° 


47' 30" 


19.6 




9° 


32.8' 


Nl4° 


20.2' 


6 Leonis. 


7m 41s 


3.16 


73° 


53' 9" 


19.5 




11° 


40.5' 


N 9° 


40.6' 


d Crateris. 


13m 6s 


3.00 


104 c 


6' 9" 


19.4 




24° 


57.4' 


S 17° 


34.7' 


<t Leonis. 


14m 41s 


3.10 


83 c 


17' 10" 


19.7 




1(1 


57.8' 


N 1° 


41.8' 


t Leonis. 


17m 24s 


3.14 


78 c 


46' 55" 


19.7 




15° 


48.6' 


N 6° 


6.2' 


t Leonis. 


21m 31s 


3.09 


86 c 


27' 20" 


19.8 




19° 


46.0' 


S 0° 


33.3' 


e Leonis. 


23m 56s 


3.07 


92 c 


18' 52" 


19.8 


TIE 


22° 


37.6' 


S 5° 


41.6' 


X Draconis; Giansar. 


23m 58s 


3.64 


19 c 


58' 47" 


19.9 


a 


8° 


34.2' 


N57° 


13.8' 


v Virginis. 


39m 26s 


3.09 


82° 


46' 13" 


20.2 


TTE 


22° 


24.8' 


N 4° 


36.1' 


/5 Leonis ; Denebola. 


42m 41s 


3.07 


74° 


43' 45" 


20.1 




19° 


53.2' 


Nl2° 


17.2' 


fi Virginis ; Zavijava. 


44m lis 


3.13 


87° 


31' 52" 


20.3 


TIE 


25° 


23.2' 


N 0° 


41.6' 


y Urs. Maj. ; Pltecda. 


47m 15s 


3.19 


35° 


36' 38" 


20 


a 


28° 


42.5' 


N47° 


8.0' 


3 Centauri. XII 


lm 53s 


3.08 


140° 


1' 38" 


20.1 


=£= 


25° 


45.3' 


S 44° 


29.9' 


a Corvi ; Alchiba. 


lm 58s 


3.08 


114 


1' 51" 


20.1 


=2= 


10 c 


30.1' 


S 21° 


44.8' 


d Crucis. IS 


7m 31s 


+ 3.14 


148° 


3' 9" 


+ 20.0 


m 


3° 


56.1' 


S 50° 


24.5' 



TABLE OF FIXED STAKS. 



MAO. 


STAR. 


: 


RT. ASCEN. 


ANN. VAR. 


N. P. D. 


ANN. VAR. 




LONG. 


LAT. 


3 


8 Urs. Maj. ; Megrez 


. XII 9m 14s 


+ 3.01s 


32° 


16' 24" 


+ 20.1s 


a 


29° 


17.9' 


N51° 


38.9' 


3 


y Corvi. 




9m 23s 


. 3.08 


106 c 


' 50' 51" 


20.0 


=£= 


8 C 


59.7' 


S 14° 


29.9' 


3-4 


i) Virginis. 




13m 31s 


3.07 


89 c 


58' 20" 


20.1 


=£= 


3 C 


5.3' 


X l° 


22.2' 


1 


a Crucis. 




19m 39s 


3.27 


152 c 


24' 18" 


19.9 


m 


10° 


8.5' 


S 52° 


51.7' 


3 


8 Corvi; Algorab. 




23m 24s 


3.11 


105° 


49' 10" 


20.1 


=== 


11° 


43.1' 


S 12° 


10.9' 


2 


y Crucis. 




24m 15s 


3.29 


146 c 


24' 41" 


20.1 


m 


4° 


59.9' 


S 47° 


48.6' 


2-3 


£ Corvi. 




27m 49s 


3.13 


112° 


42' 20" 


20.0 


=£= 


15° 


37.6' 


S 18° 


2.1' 


4 


a Muscse. 




29m 45s 


3.50 


158 c 


26' 46" 


19.9 


m 


18° 


38.7' 


S 56° 


32.4' 


3 


y Centauri. 




34m 38s 


3.28 


138° 


16' 24" 


19.9 


m 


0° 


35.6' 


S 40° 


8.8' 


4 


Y Virginis. 




35m 20s 


3.04 


90° 


45' 50" 


19.8 


=*= 


8° 


25.0' 


X 2° 


48.2' 


2 


/? Crucis. 




40m 26s 


3.46 


149° 


0' 13" 


19.7 


m 


9 C 


55.0' 


S 48° 


37.4' 


3 


e Urs. Maj. ; Alioth. 




48m 32s 


2.67 


33° 


21' 43" 


19.7 


TIE 


7° 


9.8' 


X54° 


18.5' 


3 


8 Virginis. 




49m 18s 


3.02 


85° 


55' 24" 


19.7 


=G= 


9° 


43.1' 


X 8° 


37.0' 


2-3 


a Can. Ven. ; Cor Caroli. 


50m lis 


2.82 


51° 


0' 23" 


19.6 


TTfl 


22° 


49.0' 


X 40° 


7.5' 


3 


e Virginis ; Vindciniutrix. 


55m 58s 


2.99 


78° 


22' 5" 


19.5 


=£= 


8° 


12.1' 


X 16° 


12.9' 


4-5 


a Comae Berenices. 


XI11 


'. 3m 58s 


2.92 


71° 


48' 33" 


19.2 




7° 


13.1' 


X 22° 


59.1' 


4 


r Hydra. 




12m 8s 


3.25 


112° 


30' 37" 


19.1 


=£= 


25° 


16.4' 


S 13° 


43.9' 


3 


t Centauri. 




13m 35s 


3.35 


126° 


3' 13" 


19.2 


m 


1° 


24.2' 


S 25° 


59.7' 


1 


a Virginis (Spica); Arista, 


18m 37s 


3.15 


100° 


30' 31" 


19.0 


=^ 


22° 


5.9' 


S 2° 


2.6' 


3 


C Ursse Maj oris; Mizar. 


18m 54s 


2.44 


34° 


25' 18" 


18.9 


TTfi 


13° 


55.7' 


X56° 


21.6' 


4 


Z Virginis. 




28m 20s 


3.05 


89° 


57' 22" 


18.6 


^ 


20° 


8.8' 


X 9 C 


16.0' 


3 


e Centauri. 




31m 59s 


3.75 


142° 49' 48" 


18.6 


m 


13 c 


' 49.4' 


S 39 c 


34.3' 


3-4 


v Centauri. 




42m 2s 


3.57 


131° 


3' 52" 


18.2 


m 


9° 


25.0' 


S 28° 


15.2' 


2-3 


t] Urs. Maj oris ; Alkaid. 


42m 36s 


2.35 


40° 


3' 45" 


18.1 


TTfl 


25° 


10.1' 


X54° 


23.5' 


3 


k Centauri. 




47m 45s 


3.70 


136 c 


1 40' 21" 


18.0 


TTL 


13 c 


1 12.9' 


S 32° 


55.6' 


3 


7] Bootis ; Muphrid. 




48m 44s 


2.86 


70° 


58' 30" 


18.2 


^ 


17° 


34.8' 


X 28 c 


6.1' 


1 


ft Centauri; Agena. 




55m Is 


4.17 


149 c 


1 46' 10" 


17.7 


m 


22 c 


1 3.5' 


S 44 c 


7.2' 


2-3 


Centauri. 




59m 19s 


3.50 


125° 


45' 22" 


18.1 


m 


10° 


34.2' 


S 22° 


2.2' 


3-4 


a Draconis ; Thuban. 


XIY 


lm 0s 


1.62 


25° 


1' 36" 


17.4 


TTfl 


5° 


40.5' 


X 66 c 


'J 1.5' 


4 


x Virginis. 




6m 14s 


3.19 


99° 


41' 32" 


17.1 


m 


2° 


45.0' 


X 2 C 


55.1' 


4 


i Virginis. 




9m 28s 


3.14 


95 c 


24' 10" 


17.4 


m 


2° 


2.7' 


X 7° 


13.8' 


1 


a. Bootis ; Arcturus. 




9m 58s 


2.73 


70° 


9' 57" 


18.9 


=0= 


22° 


29.3' 


X 30° 


49.5' 


4 


X Virginis. 




12m 21s 


3.24 


102° 


47' 42" 


16.8 


m 


5° 


12.5' 


x o° 


30.1' 


3-4 


Y Bootis ; Seginus. 




27m 3s 


2.43 


51° 


8' 40" 


16.0 


^ 


15° 


54.6' 


X 49° 


33.3' 


3 


i) Centauri. 




27m 35s 


3.78 


131° 


36' 31" 


16.2 


m 


18° 


30.6' 


S 25° 


29.8' 


1 


a 2 Centauri ; Ungula. 




31m 8s 


4.04 


150 c 


18' 55" 


15.1 


m 


27 c 


56.6' 


S 42° 


32.3' 


4 


a Circini. 




32m 27s 


4.77 


154° 


25' 45" 


16.1 


^ 


0° 


37.9' 


S 46° 


10.5' 


3 


a Lupi. 




33m 38s 


3.95 


136° 


51' 3" 


15.9 


m 


21° 


45.9' 


S 30° 


1.2' 


3-4 


C Bootis. 




35 m 8s 


2.86 


75° 


44' 4" 


15.7 




1° 


17.0' 


X 27° 


53.0' 


4-5 


It. Virginis. 




36m 28s 


3.15 


95° 


6' 51" 


16.0 


m 


8° 


22.5' 


X 9° 


41.7' 


3 


e Bootis ; Izar. 




39m 32s 


2.62 


62° 


23' 54" 


15.4 


^ 


26° 


21.0' 


X 40° 


38.2' 


3 


a 2 Librse ; Zubenesch. 




43m 58s 


3.31 


105° 


31' 17" 


15.3 


m 


13° 


20.9' 


X 0° 


20.9' 


3 


(1 Lupi. 




50m 21s 


3.90 


132° 


37' 47" 


15.0 




23° 


17.2' 


S 25° 


1.7' 


3 


x Centauri. 




51m 2s 


+ 3.87 


131° 


36' 3" 


14.8 


m 


23 c 


3.3' 


S 24° 


0.8' 


3 


/3 Ursse Minoris ; Kochab. 


51m 5^s 


— 0.25 


15° 


20' 3" 


+ 14.8 


a 


11° 


32.4' 


X72° 


58.5' 



ASTEONOMY. 



MAG. 

4-5 



S Librae. XIV 54m 18s • 

20 Libra}. 56m 45s 

/3 Bootis; JSFekJcar. 57m 14s 

y Triang. Australis. XV. 



2-3 ,3 Librae; Zul 



ET. ASCEN. ANN. VAR. 

3.20s 
3.50 
2.26 
5.49 
3.22 



10m 17s 



10m 28s + 2.42 
20m 57s — 0.13 
21m 13s + 3.37 
22m 9s 1.33 



27m 21s 
28m 32s 
28m 50s 



3-4 d Bootis ; Alkaturgos. 

3-4 y Ursae Minoris. 

4 C 2 Librae. 

3 £ Draconis. 

3 y Lupi- 

4 37 Librae. 
4-5 y Librae. 

3 d Serpentis. 
2-3 a Cor. Borealis ; Alphecca. 29m 24s 

4 39 Librae. 29m 26s 

4-5 fj Librae. 37m 3s 

2-3 a Serpentis ; Unukulhay. 38m 7s 

3-4 ,3 Serpentis. 40m 25s 

3 /3 Triangulis Australis. 44m 9s 

3 e Serpentis. 44m 35s 



4 X Librae. 

4 p Scorpii. 

3 y Serpentis. 

3-4 7r Scorpii. 

3 3 Scorpii. 



46m 5s 
49m 10s 
50m 4Js 
51m 17s 
52m 57s 



4-5 51 Librae. 57m 30s 

2 /3 1 Scorpii; Graffias. 58m 10s 

3 Draconis. 59m 33s 

4 v Scorpii. XVI 4m 44s 
3 <5 Opbiuci ; Yed. 7m 48s 

3 e Opbiuci. 11m 43s 

4 a Scorpii. 13ra 36s 
3-4 y Herculis. 16m 24s 
1 a Scorpii (Cor.) ; Antares. 21m 45s 
3 t] Draconis. 22m 19s 



4 Scorpn. 

2-3 /3 Herculis ; Korneforos. 

3-4 r Scorpio. 

3-4 C Opbiuci. 

2 a Triangulis Australis. 

3 £ Herculis. 
3 7] Herculis. 
3 e Scorpii. 

3 /x 1 Scorpii. 

4 (j. 2 Scorpii. 



3.27 
3.35 

2.87 
2.54 



2.95 

2.77 
5.23 
2.99 



2.77 
3.61 
3.53 

3.29 
3.48 
1.12 
3.48 
3.14 

3.17 
3.63 
2.64 
3.67 
0.82 



2.58 
3.72 
3.30 
6.29 



36m 35s 2.26 

38m 37s 2.05 

42m 4s 3.87 

43m 24s 4.05 

16 43m 52s + 4.04 



23m 13s 
24m 51s 
28m 6s 
30m 17s 
35m 27s 



N. P. D. ANN. TAR. 

98° 1' 19" + 14.6s 

114° 47' 22" 14.5 

49° 6' 67" 14.5 

158° 12' 56" 13.8 

98° 55' 14" 13.6 

56° 13' 4" 13.7 

17° 43' 15" 12.8 

106° 16' 46" 12.9 

30° 35' 44" 12.8 

130° 44' 46" 12.6 

99° 38' 5" 12.7 

104° 22' 17" 12.4 

79° 2' 28" 12.3 

62° 51' 49" 12.4 

117° 43' 10" 12.3 

105° 16' 24" 11.9 

83° 10' 48" 11.7 

74° 11' 5" 11.6 

153° 2' 28" 11.6 

85° 8' 44" 11.2 

109° 47' 30" 11.2 

118° 50' 51" 10.9 

73° 55' 42" 12.0 

115° 45' 9" 10.7 

112° 15' 50" 10.6 

101° 1' 37" 10.3 

109° 27' 41" 10.2 

31° 6' 3" 9.8 

109° 8' 1" 9.6 

93° 22' 16" 9.6 



9.2 



94° 23' 12" 

115° 17' 26" 9.( 

70° 33' 8" 8.S 

116° 9' 10" 8.4 

28° 12' 8" 8.2 

124° 25' 54" 8A 

68° 14' 10" 8.2 

117° 57' 15" 1.1 

100° 18' 43" l.t 

158° 47' 40" 1.1 

58° 10' 10" 6.8 

50° 50' 20" 7.1 

124° 3' 58" 7.( 

127° 49' 54" 6. 1 ; 
127° 48' 10" + 6.1 



LONG. LAT. 

m 13° 32.3' N 8° 15.6' 

TT, 18° 56.6' S 7° 37.3' 

=& 22° 29.1' N 54° 9.7' 

f 7° 39.4' S 48° 5.0' 

TTl 17° 37.7' N 8° 30.8' 

HI 1° 23.3' N 48° 58.8' 

Si 19° 47.9' N 75° 13.9' 

TTi 22° 9.2' N 2° 6.4' 

^ 3° 9.3' N 71° 5.8' 

TTI 29° 45.4' S 21° 13.6' 



21° 55.6' 
23° 23.4' 
16° 35.7' 
10° 31.9' 
26° 52.0' 



N 8° 
N 4° 
N 28° 
N 44° 



55.3' 
24.0' 
53.8' 
20.3' 
29.4' 



25° 36.5' N" 4° 1.1' 

20° 19.0' N 25° 31.9' 

TIL 18° 11.5' N 34° 20.6' 

^ 10° 6.3' S 41° 54.6' 

Til 22° 34.4' N 24° 1.9' 

Til 28° 43.9' N 0° 6.2' 

t 1° 15.5' S 8° 36.2' 

TTI 20° 59.9' N 35° 15.6' 

$ 1° 11.7' S 5° 27.4' 

$ 0° 49.6' S 1° 58.1' 

TTI 29° 33.7' N 9° 15.2' 

$ 1° 26.7' N 1° 1.4' 

^ 14° 56.0' N 74° 26.0' 

^ 2° 53.9' N 1° 39.1' 

0° 33.3' N 17° 15.8' 

1° 45.6' N 16° 27.3' 

^ 6° 3.3' S 4° 1.1' 

Til 27° 27.9' N 40° 1.2' 

f .3° 1.1' S 4° 33.1' 

£= 12° 40.1' N 78° 27.5' 

^ <r 43.7' S 12° 39.7' 

Til 29° 48.6' N 41° 51.7' 

f 9° 42.8' S 6° 6.1' 

7° 29.0' N 11° 24.5' 

# 19° 9.0' S 46° 7.9' 

TTL 29° 44. 8' N 57° 53.7' 

TTI 27° 1.4' N 60° 18.5' 

f 13° 36.9' S 11° 42.7 r 

14° 24.8' S 15° 24.3' 

# 14° 30.1' S 15° 21.8' 



TABLE OF FIXED STARS. 



51 



MAG. 

4-5 



3-4 
3-4 
3-4 



s Algethi. 



Z 1 Scorpii. 
C 2 Scorpii. 
c Ophiuci. 
e Herculis. 
f) Scorpii. 

7] Ophiuci. 
C Draconis. 
a Herculis ; 
«; Herculis. 
Ophiuci. 

Y Arse. 
/J Arse. 
d Ophiuci. 



\ o Scorpii. 

X Scorpii ; Lesath. 
I i? Draconis ; Alwaid. 
6 Scorpii. 

a Ophiuci ; Rasalague. 
x Scorpii. 

/? Ophiuci ; Celhelrai. 
^Scorpii. 

f Draconis ; Grumium. 
y Draconis; Etanin. 
67 Ophiuci. 



ET. ASCEN. ANN. VAR. 

XVI 45m 10s + 4.20s 
45m 47s 4.20 
48m 6s 



55m 30s 



2.2D 



XVII 3m lis 4.27 



3m 13s 
8m 26s 
8m 57s 
10m 42s 
14m 20s 

14m 53s 
14m 55s 
19m 22s 



27m 36s 
28m 20s 
29m 8s 
33m 51s 

37m 18s 
38m 51s 
51m 22s 
53m 42s 
54m 24s 



3.43 
0.16 
2.73 
2.09 
3.68 

5.03 



4.07 
1.35 
4.30 
2,78 
4.15 

2.96 
4.20 
1.04 
1.39 
3.01 



4 ^Sagittarii. 57m 2s 3.84 

4 f 2 Sagittarii. 57m 47s 3.86 

3-4 tx Sagittarii. XVIII 6m 17s 3.59 

4 i) Sagittarii. 9m 10s + 4.06 

3 3 Ursae Minoris. 11m 10s —19.45 



3-4 d Sagittarii. 12m 59s 

3 e Sagittarii ; Kaus Aust. 15m 53s 

4 a Telescopii. 17m 42s 
4 X Sagittarii. 20m 15s 
1 a Lyrae ; Vega. 32m 42 s 

3 /5 Lyrae ; Sheliak. 45m 28s 

3 <t Sagittarii. 47m 31s 
4-5 Serpentis ; Alga. 50m 0s 

4 f 2 Sagittarii. 50m 16s 
3-4 e Aquilae. 53m 57s 

3 y Lyrae; Sulaphat. 54m 16s 
3-4 £ Sagittarii. 54m 39s 

4 t Sagittarii. 59m 28s 
3 I Aquilae. 59m 37s 

3 C Aqn\\.; Deneb El Okab. 18 59m 40s ■ 



3.84 
3.99 
4.45 
3.71 
2.03 



2.98 

3.58 
2.72 

2.24 
3.83 
3.75 



N. P. D. ANN. VAR, 

132° 9' 11" + 6.6s 

132° 8' 47" 6.8 

79° 37' 39" 6.3 

58° 53' 18" 5.6 

133° 4' 18" 5.2 



53° 2' 54" 
114° 52' 21" 

146° 15' 24" 
145° 24' 33" 
119° 45' 8" 
139° 46' 27" 
127° 11' 32" 

127° 0' 33" 
37° 36' 20" 

132° 55' 0" 
77° 20' 51" 

128° 57' 48" 

85° 22' 43" 



87° 3' 39" 

119° 35' 3" 
120° 25' 25" 
111° 5' 21" - 
126° 47' 56" 
3° 23' 33" 

119° 52' 45" 
124° 26' 30" 
136° 2' 12" 
115° 29' 20" 
51° 19' 54" 

56° 46' 54" 
116° 26' 59" 

85° 57' 26" 
111° 16' 7" 

75° 6' 2" 

57° 28' 49" 
120° 3' 24" 
117° 51' 2" 
95° 4' 5" 
76° 19' 15" - 



LONG. LAT. 

t 15° 22.7' S 19° 38.3' 

15° 29.8' S 19° 37.0' 

8° 53.9' X 32° 31.6' 

6° 34.7' X 53° 15.9' 

18° 59.6' S 20° 9.3' 

t 16° 12.4' N 7° 12.7' 

=£= 1° 26.5 X 84° 46.0' 

t 14° 15.9' X 37° 17.0' 

10° 19.1' N 59° 33.4' 

19° 39.0' S 1° 49.5' 

22° 32.9' S 33° 5.5' 

22° 25.4' S 31° 54.9' 

21° 8.1' S 6° 36.7' 

23° 11.4' S 26° 32.4' 

22° 16.1' S 13° 59.2' 

22° 50.5' S 13° 46.1' 

10° 12.5' N 75° 17.7' 

23° 51.3' S 19° 38.1' 

20° 41.8' N 35° 51.7' 

24° 38.8' S 15° 37.3' 

23° 35.7' X 27° 57.1' 

25° 46.7' S 16° 41.8' 

23° 0.8' N 80° 15.4' 

26° 13.7' X 74° 58.0' 

28° 26.2' X 26° 24.0' 

29° 21.2' S 6° 7.4' 

# 29° 31.1' S 6° 57.8' 

\3 1° 29.1' X 2° 21.9' 

\3 1° 53.3' S 13° 20.7' 

H 29° 27.3' X 69° 55.8' 

\3 2° 50.0' S 6° 27.1' 

3° 20.1' S 11° 1.8' 

3° 19.5' S 22° 37.8' 

4° 34.4' S 2° 6.6' 

11° 55.2' X 61° 49.5' 

17° 9.0' X 56° 0.0' 

10° 38.2' S 3° 25.8' 

14° 0:6' X 26° 53.6' 

11° 42.3' X 1° 40.8' 

16° 31.5' X 37° 35.2' 

20° 11.4' X55° 1.8' 

11° 53.6' S 7° 9.7' 

13° 5.6' S 5° 3.7' 

15° 35.5' X 17° 35.2' 

V3 18° 3.4' X 36° 12.4' 



52 



ASTEOJOYT. 



STAB. EX. ASCES - . A2C3T. TAB. 

a Coronse Australia M X Om 58e 

s SagittariL 2m 20s 3.5 < 

d Draconis. 12m 31s 0.04 

^Sagitt.; Uriah w BamDu 13m 39s 4.33 
p 2 SagittariL 14m 10s 4.33 

a Sagitt; Ruchbah urRamih 15m 14s 4.18 
a Vulpeeulae et Anseris. 23m 30s 2.49 
/3 Cygni ; - 25m 41s 2.42 

a Sagittse (The Arrow). 34m 31s 2.6S 
r Aquilse; Tarazed. 40m 19a 

3 Cvjrm. 41m 4s 1.88 

a Aquilae : _i U -.'-. 44m 41s 

,5 Aquilae ; Alskain. 49m 10s 

c SasrittariL 54m 58s 

aiCapricor; Deskabeh.XX. 10m 43s 

a 2 Capricor ; Secunda Giedi. 11m 7s 
Capricorni; Dabih, 13m 59s 

a Pavonis (Oeulus). 15m 45s 

j Cv^ri . l' m 45s 

t. Capricorni. 20m 10s 

28m 46s 
31m 42s 
32m 56s 
33m 36s 
33m 50s 



3 a Indi. 

4 ,3 Delphini; Roianen. 

5 v Capricorni. 

3 Pavonis. 
3-4 a Delphini; Svalocin. 

1 a Cygni; Deneb. 

4-5 d> Capricorni 

4—5 s AquariL 

4 3 Aquarii. 
3 £ Cygni; Giendh. 

4—5 a Mieroscopii. 

5 r t Capricorni. 
5-6 61 Cygni. 
3 " Cygni. 
4-5 a Equolei. 



37m 10s 
3Sm 42s 
40m 55s 
41m 9s 
41m 9s 

42m 10s 

57m 17s 

XXT lm 18s 



: Capricorni 15m 17s 

a Cephei ; Alderamin. 15m 5 

y Pavonis. 

Z Capricorni. 

/3 Aquarii; Saddlsund. 

/S Cephei; Alphirk. 
Y Capricorni. 
s Peea> : ; 
x P^gasi. 
8 Capricorni 



2.95 
3.70 
3.33 



2. SI 
3.43 
5.49 



3.43 
2.69 
2.55 



K. P. D. A2TS. VAX. 

- t8*— 5.1s 

111° 13' 11* 5.4 

22= 33' 31* 6.3 

134= 41' 36" 6.1 

135- 2' 4' 6.2 



S3 : 54' 18* 8.6 

102 = 53' 35' 10.7 

102 = 55' 51" 10.8 

105 = 10' 28* 11.0 

147 = 7' 53' 11.2 

3 c' 11.3 

108° 37' 11* 11-5 



S = 34' 37 
6° 39' 0' 
4° 31' 39' 

9' 56' 
43' 8' 



-■ 



■ - 
56° 29' 50' 

124= 14' 32' 
110° 20' 53' 
51° 51' 51' 
60= 17' 6' 
85* 16' 5* 

107 = 21' 55" 



16m 5s 


5.05 


155' 


55' 53' 


19m 32s 


3.44 


112° 


57' 5' 


24m 59s 


3.17 


96= 


7' 12' 


27m 2s 


O.SO 


19= 


57' 17' 


33m 10s 


3.34 


107= 


13' 33' 


38m 3s 


2.95 


80° 


41' 50' 


38m 59s 


2.71 


64= 


55' 44' 


40m Ss 


4- 3.3 


106 : 


1 41' 36' 



12.4 SS 



■LOSG. LAT. 

\5 12= 23.2' S 15= 17.5' 

V3 14= 30.4' N 1= 27.4' 

°P 15= 32.6' X S2= £.3.0' 

\3 14= 1.6' S 22= 7.7' 

14= 4.7' S i. ; .- - 

14= 53.3' S 18° 21.4' 

27° 46.7' X 45° 52.6' 

29° 31.1' 2S 4S= 5S.9' 

29= 20.2' N" 3£ - - " 

V3 29= 12.0' ZS 31= 15.5' 

SS 14° 31.7' N 64° 25.8' 

0= 0.5' 2S ■-■ L8.4 

SS 0= 41.2' N 26= 41.4' 

Y3 25= 19.1' S 7= 5.5' 

SS 2= 1.5' N " 

2= 6.7' X 6= 56.6' 

SS 2= 18.1' X 4= 36.6' 
A3 22= 4.1' S 36= 14.S' 

SS 23= 7.3' N57° S.0' 

St 2= 58.1' ?S 0= 54.8' 

\5 27= 21.1' S -~ 

~ 14= 36.1' > 31° 55.9' 

SS 5= 55.1' S '14.2 
\3 20= 44.5' S 45= 56.4' 
15= 38.5' X 33= 8.1' 



15.7 
16.0 



- N 59= 58.0' 

5° 21 S 1° 0.6' 

- - - N S= 5.6' 

11° 13.4' X 12= 23.5' 

25= 59.4' X 49= 25.5' 



S 15= 26.2' 
S_ 2 : 58.2' 
6 X 51= 52.3' 
I |8.S N 43 = 42.2' 
X 20= S.2' 



:: 



SS 21= 26. 

- 15= 56.1' S 1= 21.4' 

=p 11° 3.9' S - ' - ' 

V3 26= 49.4' S 46= 59.2' 

SS 15° 11-4' S 6° 58.9' 

SS 21= 39.1' N 8= 37.5' 

y 3° 50.4' N" 1 

SS 20= 2.3' S 2 

5£ 0= 8.7' N 22= 6.5' 

y. 7= 12.0 > 36= 3S.6' 

-; 21= 47.7 S 2= 34.6' 



TABLE OF FIXED STAES. 



MAG. STAR. ET. ASCEN. ANN. VAR. 

3 y Grais. XXI 46m 22s + 3.67s 

3 a Aquarii; Sadalmelik. 59m 22s 3.08 

4-5 ( Aquarii. 59m 41s 3.25 

2 a Gruis. XXII 0m 20s 3.81 

3 a Tucanse (Am. Goose). 9m 55s 4.17 

4-5 Aquarii. 10m 14s 3.17 

3 y Aquarii. 15m 12s 3.11 

4 C Aquarii. 22m 24s 3.09 
4 j3 Piscis Australis. 24m 24s 3.44 
4 a Lacertse (The Lizard). 26m 9s 2.46 

4 t] Aquarii. 28m 56s 3.09 

3 (3 Gruis. 35m 12s 3.61 

3 £ Pegasi ; Homan. 35m 14s 2.99 

3 tj Pegasi; Matar. 37m 9s 2.80 

4 p. Pegasi. 43m 58s 2.89 

4 X Aquarii. 46m 5 s 3.13 
3 8 Aquarii; Scheat. 48m Is 3.19 

1 a Piscis Aust. ; Fomalhaut. 50m 44s 3.33 

5 /? Piscium. 57m 31s 3.06 

2 (3 Pegasi; Scheat, 57m 43s 2.90 

2 a Pegasi ; Markab 58m 32s 2.98 
4-5 c* Aquarii. XXIII 2m 47s 3.21 
4-5 y Piseium. 10m 41s 3.11 
4-5 i Piscium. 33m 32s 3.11 

3 y Cephei; Er Bai. 34m 14s 2.41 



5 X Piscium. 

5 f 1 Octantis. 

4-o (a Piscium. 

4-5 30 Piscium. 

4 2 Ceti. 



23 



35m 40s 
44m 37s 
52m 54s 
55m 33s 
57m 20s 



136» The annual variations in Right Ascension 
and North Polar distance, are themselves subject 
to a small change ; that is, the variation is not the 
same in amount every year ; it increases or de- 
creases, as the star apparently approaches the pole 
or recedes from it. There are, however, only two 
stars among the 364 here catalogued, whose differ- 
ences of variation are sufficiently great to require 
notice in ordinary calculations ; they are both very 
near the North Pole (Sec. 45) in the constellation 
Ursa Minor ; Alruccabali, the pole star, increases 
its annual variation yearly, at the rate of 0.1143 



N. P. D. ANN. VAR. 

127° 57' 10" — 16.5s 

90° 55' 35" 17.3 

104° 28' 31" 17.2 

137° 33' 55" 17.1 



LONG. 

15° 39.1 



LAT. 



150° 



>2 52 



17.7 



9.8' S 23° 2.3' 

X 1° 36.6' N 10° 40.1' 

£? 26° 58.3' S 2° 4.4' 

14° 9.0' S 32° 53.6' 

X? 7° 55.1' S 45° 23.4' 



98° 24' 18" 17.7 X 1° 30.8' N 2° 43.0' 

92° 0' 59" 18.0 4° 57.9' N 8° 14.6' 

-90° 39' 31" 18.3 3£ 7° 9.5' N 8° 50.0' 

122° 59' 14" 18.3 ^ 25° 25.6' S 21° 21.5' 

40° 21' 36" 18.3 T 6° 24.9' N 53° 17.1' 

90° 45' 40" 18.4 X 8° 39.5' N 8° 9.3' 

137° 32' 17" 18.6 JXC 20° 33.9' S 35° 25.2' 

79° 49' 13" 18.7 X 14° 24.6' 1ST 17° 4.1' 

60° 25' 55" 18.7 23° 58.9' N 35° 6.6' 

66° 3' 28" 18.9 22° 38.7' N 29° 23.8' 



98° 


14' 39" 


19.0 


9° 


49.8' 


S C 


23.0 


106 c 


29' 5" 


19.1 


7 C 


7.7' 


S 8 C 


11.1 


120° 


17' 3" 


19.0 


2° 


5.9' 


S 21° 


7.0 


86° 


51' 9" 


19.3 


16° 


50.6' 


N 9 C 


3.3 


62° 


35' 40" 


19.5 


27° 


37.6' 


N31 c 


9.5 



75° 28' 0" 19.3 21° 44.7' N 19° 24.5' 

111° 50' 59" 19.5 8° 16.0' S 14° 29.1' 

87° 24' 1" 19.6 19° 40.8' N 7° 16.2' 

85° 3' 4" 19.5 ^ 25° 53.7' N 7° 10.5' 

13° 3' 54" 20.1 b 28° 21.1' 1ST 64° 38.9' 

88° 54' 27" 19.8 X 24° 51.1' N 3° 25.2' 

175° 42' 50" 20.0 YS 10° 31.2' S 65° 53.7' 

83° 49' 43" 20.0 T 0° 50.2' N 6° 22.0' 

96° 42' 31" 20.0 X 26° 18.1' S 5° 42.6' 

108° 1' 53" — 20.1 X 22° 1.0' S 16° 14.1' 

sec. in Right Ascension, and the Annual Variation 
in North Polar Distance of d TJrsae Minoris changes 
at the rate of 0.028" yearly. Both these variations 
are additive for subsequent years, and subtractive 
for preceding years, to or from the places as found 
by the table — the correction here given being 
multiplied into half the square of the time in years 
before or after the epoch of the tables. 

The declination of a star is readily known when 
the north polar distance is given. Thus: 

90° — North Polar Dis.= the Dec ; North. 

North Polar Dis. — 90° = the Dec ; South. 



DEFrNE and explaiu (the figures refer to the sections) : 

135. Table of Fixed Stars ; Ann. Variation in Rt. Asa, N. P. D., and Lon. 136. Change in Ann. Variation ; Declination. 



CULMINATING, RISING, AND SETTING. 



137. If from the Right Ascension of a star as 
given in the preceding table, (adding 24 hours, if 
required) we subtract the right ascension of the 
Sun at any required date (Sec. 33), the remainder 
will express the time that the Sun will pass the 
meridian above the earth, before the star, on the 
day in question ; it is, therefore, the time after solar 
noon when the star culminates, or passes the meri- 
dian. If we correct this remainder by the equa- 
tion of time (Sec. 34), it will give the hours and 
minutes past clock noon when the star culminates. 
Every star, the North Polar Distance of which is 
greater than the distance of the spectator from the 
North Pole of the earth, crosses the meridian South 
of the Zenith ; hence the meridian passage, or cul- 
mination of a star, is often called " Southing." 

138. To find the time of Rising and Setting of a 
star, necessitates a more lengthy operation. When 
the Sun is on the Equinoctial — near March 20th 
and September 23rd — the days and nights are 
equal all over the globe, excepting the increase 
always made in the length of the day by the refrac- 
tion of the Sun's rays, which causes him to appear 
to rise earlier and set later, by a few minutes each 
d;iy, than would be the case were not the solar 
rays bent downward a little in passing through the 
atmosphere. At the earth's equator he rises 6 
hours and a few minutes before noon, and sets six 
hours and a few minutes after solar noon ; but at 
any place between the Equator and the Poles, the 
difference between the length of the day and 12 
hours increases with the Sun's declination, and 



with the same declination the difference increases 
with the latitude of the place of observation. 

The Sun is longer above the earth than below it, 
at any given point on the earth's surface, when his 
declination is of the same name as the latitude of 
the place ; and is longest below the horizon when 
his declination is different from the latitude. The 
United States are in North latitudes ; therefore, 
when the Sun has North declination — from April 
to September — the days are longest ; from Octo- 
ber to March the Sun's declination is South, and 
the nights are longest (Sec. 17). The same differ- 
ence is met with in noting the times of rising and 
setting of the fixed stars. 

To an observer in North latitude 40°, the North 
Pole is always 40° above the horizon, and stars 
within 40° of the pole never sink below the horizon, 
being above it when they cross the lower meridian, 
as in the case of the Dipper (Sees. 36 and 40). 
The greater the North Polar Distance beyond this 
limit, the more time is occupied in the passage 
below the horizon ; and stars, the North Polar dis- 
tances of which are greater than 180° minus the 
latitude, are always below the horizon. A star on 
the Equinoctial is 12 hours above the earth, and 
12 hours below it ; the passage from the horizon to 
the meridian being measured by 6 hours, or (its 
equivalent) 90° of a great circle. 

130. In the accompanying diagram let N S 
represent the horizon ; P the North Pole, elevated 
above the horizon by an amount equal to the lati- 
tude of the place — say 40° ; I, the South Pole ; Z, 



PASSING THE MERIDIAN AND HORIZON. 



55 



the Zenith ; A B, the Equinoctial ; E, the Eastern 
point of the horizon; T, the place of a star on the 




horizon. The angle E P A is equal to 90° ; that 
is, a star at E would arrive at A in 6 hours after- 
wards. A meridian circle through the star at T, 
would cut the Equinoctial at D ; and the Arc E D, 
measured by the angle E P D, is the excess over 
90° of the angle APD. In the spherical triangle 
E D T, we have given the angle at E (equal to 
90° minus the latitude of the place), the right angle 
at D, and the side D T (equal to the declination 
of the star). Taking the side D E as the middle 
part, we have, by the Napieran analogy : 

Cotangent of Angle E, multiplied into Tangent 
of D T, equals Sine of D E ; or, 

Log Tan of Latitude of Place, plus Log Tan of 
Star's Declination, equals the Log Sine of the Dif- 
ference. 

This difference, added to 90°, will give the arc 
D A, which, divided by 15 (Sec. 26), will give the 
hours and minutes required for a star to move from 
D to A, or from T to M. 

It is apparent, from the diagram, that if the star 
were at t, with the same amount of declination 
South from A B, the difference above found would 



need to be subtracted from 90° to find the time of 
passage from the horizon to the meridian above 
the earth. It is manifest, also, that a star at V 
would be above the horizon during every part of 
its daily circuit ; and a star at W, or at any point 
South of the circle S K, would never appear above 
the horizon. 

140. The table on the next page is constructed 
in accordance with the above rule, and from it may 
be found, nearly, the difference in time between the 
horizon and meridian passage of any star. Look 
for the declination of the star in the first column, 
and find the Latitude of the place of observation at 
the top of the table. The difference will be found 
at the angle of meeting, proportion being made 
when the quantities used as arguments are inter- 
mediate to those given in the head and left hand 
column. Then : 

141. If the place of observation be in North 
latitude, as is the case in the North American con- 
tinent and Europe; the Semi-Diurnal Arc, or mea- 
sure of the passage between the meridian and hor- 
izon, or horizon and meridian, is thus found : 

If the Declination be North, add the tabular dif- 
ference to 6 hours ; 

If the Declination be South, subtract the tabular 
difference from 6 hours ; 

The result is the Semi-Diurnal Arc. The rule 
reversed will give the arc for South latitudes. 

Subtract the Semi-diurnal Arc from the time of 
culmination, the remainder is the time of rising ; 
add the arc to the time of culmination, the sum is 
the time of setting. 

142. The arc and times thus found, make no 
allowance for refraction (Sec. 138) the effect of 
which is to make a star visible on the horizon while 
it is yet about 0° 35' below the line. This distance 
is, of course, measured perpendicularly from the 
horizon, and, as the stars rise and set more or less 
obliquely as the distance from the pole is less or 



56 ASTRONOMY 



TABLE OF DIFFERENCES, 

For finding the Ascensional Difference, from the Declination of a heavenly body and the 
Latitude of the place of observation. 

10° 20° 30° 35° 38° 40° 42° 44° 46° 48° 50° 52° 54° 56° 58° 60° 

2° 01030506060707 0808090 10 10 11 12 13 14 

4° 3 6 9 11 12 13 14 15 17 18 19 21 22 24 26 28 

6° 4 9 14 17 19 20 22 23 25 27 29 31 33 36 39 42 

8° 6 12 19 22 25 27 29 31 33 36 39 41 45 48 52 56 

10° 7 15 23 28 31 34 37 39 42 45 49 52 56 1 01 1 06 1 11 

12° 9 18 28 34 38 41 44 47 51 55 59 1 03 1 08 1 13 1 19 1 26 

14° 10 21 33 40 45 48 52 56 1 00 1 04 1 09 1 14 1 20 1 27 1 34 1 42 

16° 12 24 38 46 52 56 1 00 1 04 1 09 1 14 1 20 1 26 1 33 1 41 1 49 1 59 

18° 13 27 44 53 59 1 03 1 08 1 14 1 19 1 25 1 31 1 38 1 46 1 55 2 05 2 17 

20° 15 30 49 59 1 06 1 11 1 17 1 22 1 29 1 36 1 43 1 51 2 00 2 11 2 22 2 36 

22° 16 34 54 1 06 1 14 1 19 1 26 1 32 1 39 1 47 1 55 2 05 2 15 2 27 2 41 2 58 

24° 18 37 1 00 1 13 1 21 1 28 1 35 1 42 1 50 1 59 2 08 2 19 2 31 2 45 3 02 3 22 

26° 20 41 1 06 1 20 1 30 1 37 1 44 1 52 2 01 2 11 2 22 2 35 2 49 3 05 3 25 3 51 

28° 21 45 1 12 1 27 1 38 1 46 1 55 2 04 2 14 2 25 2 37 2 52 3 08 3 28 3 53 4 28 

30° 23 49 1 18 1 35 1 47 1 56 2 06 2 16 2 27 2 40 2 54 3 11 3 30 3 55 4 30 6 00 

32° 25 53 1 25 1 44 1 57 2 06 2 17 2 29 2 41 2 56 3 13 3 32 3 57 4 32 6 00 

34° 27 57 1 32 1 53 2 06 2 18 2 30 2 43 2 57 3 14 3 34 3 59 4 33 6 00 

36° 29 1 01 1 39 2 02 2 18 2 30 2 43 2 58 3 15 3 35 4 00 4 34 6 00 

38° 32 1 06 1 47 2 13 2 30 2 44 2 59 3 16 3 36 4 01 4 34 6 00 

40° 34 1 11 1 56 2 24 2 44 2 59 3 16 3 37 4 01 4 35 6 00 

42° 37 1 17 2 05 2 36 2 59 3 16 3 37 4 02 4 35 6 00 

44° 39 1 22 2 16 2 50 3 16 3 37 4 02 4 35 6 00 

46° 42 1 29 2 27 3 06 3 36 4 01 4 35 6 00 

48° 45 1 35 2 40 3 24 4 01 4 35 6 00 

50° 49 1 43 2 54 3 46 4 34 6 00 



52 


1 51 


3 11 


4 15 6 00 


56 


2 00 


3 30 


4 58 


1 01 


2 11 


3 55 




1 06 


2 23 


4 30 




1 11 


2 36 


6 00 




1 17 


2 53 




When 


1 25 


3 13 




ris* 



When the Sum of the Latitude and Declination exceeds 90° the Star neither 
sets ; being always above the horizon or always below it. 



EIGHT ASCENSION, AND DECLIIATIOK. 



57 



greater, the time required for a star to rise through 
that perpendicular space varies with the latitude 
of the place of observation, and also with the decli- 
nation. The following are the corrections in time 
due to horizontal refraction, for each 10° of latitude 
and declination : 



CORRECTIONS FOR REFRACTION. 



cr 



10° 20° 



40° 50° 60° 70° 



0° 2 20 2 22 2 30 2 42 3 03 3 38 4 40 6 41 

10° 2 22 2 24 2 31 2 48 3 06 3 41 4 44 6 47 

20° 2 30 2 31 2 38 2 52 3 14 3 52 4 58 

30° 2 42 2 48 2 52 3 07 3 31 4 12 

40° 3 03 3 06 3 14 3 31 3 59 



143. This correction always increases the semi- 
diurnal arc ; it must, therefore, be subtracted from 
the already computed time of rising, and added to 
the time of setting, as found from the rule in Sec. 
141. In the case of the fixed stars, the mere 
observer needs not to take this correction into 
account, as the stars are very seldom discernible 
within two or three degrees of the horizon. 

In the case of the Sun, this correction being 
applied, will give the time when his center will 
appear to be on the horizon. If we wish to find 
the time when either edge of the Sun will touch 
the visible horizon, we must make a still further 
correction for his semi-diameter, which averages a 
little more than 0° 16', or about 46 hundredths of 
the perpendicular refraction. The tabular refrac- 
tion being therefore augmented by nearly one half, 
will give the refractive correction for the Sun's 
upper edge ; and diminished nearly one half, will 
be the refractive correction for his lower edge. 

144. To find the length of the day from the 
preceding tables, requires a knowledge of the Sun's 
declination. It may be found from the table on 
the next page, which gives the right ascension and 
declination of every fifth degree of the Ecliptic, 
and for 5° of latitude North and South. 

To find the Right Ascension of an object within 



8° or 10° of the Ecliptic : Look for the nearest lon- 
gitude in the fourth column of the Table. Then : 

If the Longitude be in the first six signs, find the 
Right Ascension, without latitude, corresponding 
thereto, by proportion between the values in the 
second column. 

If the object have north latitude, a comparison 
with the first column will show how much should 
be added or subtracted for 5° of latitude, and a 
proportionate quantity can be applied for the lati- 
tude given. If the object have South latitude, 
compare with the third column for the correction. 

If the longitude be in the last six signs, find the 
right ascension without latitude, as before ; com- 
pare with the third column for North latitude, and 
with the first column for South latitude. Then 
add 12 hours to the corrected quantity. 

For Declination : Look for the longitude as be- 
fore, in the fourth column ; if the object be with- 
out latitude (as, the Sun), the declination * will be 
found by proportion between the numbers in the 
sixth column ; it will be North declination for the 
first six signs, and South for the last six. 

If the object have North latitude, compare with 
the fifth column for the first six signs, and with 
the seventh column for the last six. For South 
latitude, compare with the seventh column for the 
first six signs, and with the fifth column for the 
last six. Where the declination in the table is 
marked — , the correction for 5° of latitude changes 
the declination to the other side of the Equinoctial, 
making it North instead of South, and vice versa. 

145. Example : Find the times of culmination, 
rising, and setting of the Sun, Aldebaran, and Sir- 
ius, for May 20th, in North latitude 40° : 



Proportionating : his right ascension, May 20th, 
is about 3h. 40m. 40s. Add to this the Equation 



58 ASTRONOMY. 

The following is a table for finding Right Ascension and Declination from Longitude and Latitude. 



EIGHT ASCENS 


ION. 


LONGITUDE. 








T to ^ 5° N. 
i to T 5° S. 


ECLIPTIC. 


T to =fl= 5° S. 

=£= to T 5° K 




h. m. s. 

23 52 4 


h. m. s. 



7 56 


°P =2= 0° 


10 24 


18 21 


26 17 


5° 


28 44 


36 45 


44 39 


10° 


47 20 


55 14 


1 2 59 


15° 


1 6 4 


1 13 51 


1 21 23 


20° 


1 25 3 


1 32 38 


1 39 59 


25° 


1 44 20 


1 51 37 


1 58 40 


8 m o° 


2 3 48 


2 10 51 


2 17 36 


5° 


2 23 36 


2 30 20 


2 36 44 


10° 


2 43 52 


2 50 7 


2 56 6 


15° 


3 4 20 


3 10 12 


3 15 43 


20° 


3 25 14 


3 30 34 


3 35 32 


25° 


3 46 32 


3 51 15 


3 55 38 


n t o° 


4 8 10 


4 12 13 


4 15 57 


5° 


4 30 6 


4 33 26 


4 36 29 


10° 


4 52 20 


4 54 52 


4 57 12 


15° 


5 14 46 


5 16 29 


5 18 4 


20° 


5 37 18 


5 38 12 


5 39 


25° 


6 


6 


6 


2>V3 0° 


6 22 42 


6 21 48 


6 21 


5° 


6 45 14 


6 43 31 


6 41 56 


10° 


i 7 40 


7 5 8 


7 2 48 


15° 


7 29 54 


7 26 34 


7 23 31 


20° 


7 51 50 


7 47 47 


7 44 3 


25° 


8 13 28 


8 8 45 


8 4 22 


a xxf o° 


8 34 46 


8 29 26 


8 24 28 


5° 


8 55 40 


8 49 48 


8 44 17 


10° 


9 16 8 


9 9 53 


9 3 54 


15° 


9 36 24 


9 29 40 


9 23 16 


20° 


9 56 12 


9 49 9 


9 42 24 


25° 


10 15 40 


10 8 23 


10 1 20 


m X 0° 


10 34 57 


10 27 22 


10 20 1 


5° 


10 53 56 


10 46 9 


10 38 37 


10° 


11 12 40 


11 4 46 


10 57 1 


15° 


11 31 16 


11 23 15 


11 15 21 


20° 


11 49 36 


11 41 39 


11 33 43 


25° 


12 7 56 


12 


11 52 4 


=2= T 0° 



DECLINATION. 



T to ^ 5° N. 


=== to T 5° S. 


4 


35' 


6 


35 


8 


34 


10 


31 


12 


26 


14 


22 


16 


8 


17 


53 


19 


32 


21 


7 


22 


34 


23 


53 


25 


2 


26 


4 


26 


54 


27 


35 


28 


5 


28 


22 


28 


27 


28 


22 


28 


5 


27 


35 


26 


54 


26 


4 


25 


2 


23 


53 


22 


34 


21 


7 


19 


32 


17 


53 


16 


8 


14 


22 


12 


26 


10 


31 


8 


34 


6 


35 


4 


35 



ECLIPTIC. 


T to === 5° S. 
=£= to T 5° K 


0° 





—4° 


35' 


2 





—2 


36 


3 


58 


—0 


38 


5 


55 


1 


18 


7 


50 


3 


10 


9 


41 


5 


2 


11 


29 


6 


48 


13 


12 


8 


29 


14 


50 


10 


5 


16 


21 


11 


34 


17 


46 


12 


56 


19 


2 


14 


11 


20 


10 


15 


16 


21 


9 


16 


14 


21 


58 


17 


2 


22 


37 


17 


38 


23 


5 


18 


5 


23 


22 


18 


22 


23 


27 


18 


27 


23 


22 


18 


22 


23 


5 


18 


5 


22 


37 


17 


38 


21 


58 


17 


2 - 


21 


9 


16 


14 


20 


10 


15 


16 


19 


2 


14 


11 


17 


46 


12 


56 


16 


21 


11 


34 


14 


50 


10 


5 


13 


12 


8 


29 


11 


29 


6 


48 


9 


41 


5 


2 


7 


50 


3 


10 


5 


55 


1 


18 


3 


58 


—0 


38 


2 





— 2 


36 








—4 


35 



TIMES OF RISING AND SETTING. 



59 



of Time (Sec. 34), which is 3in. 20s. ; the sum is 
Sidereal, or Star Time, at noon of May 20th=3h. 
53m. — omitting the seconds. 

Sidereal time being the right ascension on the 
meridian at clock noon, and the Sun's right ascen- 
sion being less than that of the meridian, the Sun 
has passed the South line, 3m. 20s. at clock noon ; 
that is, he culminates at llh. 56m. 40s. A.M., on 
the day in question. 



The Sun's declination is (Sec. 144) about 20°5' 
North. The difference (Sec. 140) is lh. ll^m. ; 
the refraction (Sec. 142) is 3^m. The sum of these 
added to 6 hours, gives the semi-diurnal arc of the 
Sun's center = 7h. 14^m. This subtracted from 
llh. 56£m. A.M., gives 4h. 42m. A.M. for the time 
of Sunrise, and added to llh. 56|m., gives 7h. 
11m. P.M. for the time of Sunset. Allowing l|m. 
(Sec. 143) for the Sun's semidiameter, we have : 



Rising; Upper edge 4h. 40£m. A.M. — Center 4h. 42m. A.M. 

Setting; Lower edge 7h. 9£m. P.M. — Center 7h. 11m. P.M. 

From Table North Polar Distances Aldebaran 

Declinations (Sec. 136) 
Differences in Latitude 40° North - 
Semi-diurnal Arc .... 

Refraction 3m., add, gives 



— Lower edge 4h. 43£m. A.M. 
-Upper edge lh. 12£m. P.M. 



73° 45' 


Sirius 


106° 


33' 


16° 15' North. 


" 


16° 


33' South. 


Oh. 57m. 


" 


Oh. 


58m. 


6h. 57m. 


" 


5 b 


02m. 


lh. 00m 


" 


5h. 


05m. 



4h. 29m. 
3h. 53m. 



Oh. 36 P.M. 

7h. 00m 



2h. 47 P.M. 
5h. 05m. 



5h. 36 A.M. 
7h. 36 P.M. 



9h. 42 A.M. 
7h. 52 P.M. 



Right Ascensions - 

Sidereal Time, Subtract - 

Time of Culmination - - - - 
Corrected Semi-diurnal Arc 

Subtract; gives Rising - 
Add ; gives time of Setting 

146. The times of Rising and Setting are thus 
easily found to within a minute or two of the truth, 
which is near enough for most purposes. When, 
however, it is wished to be exact, the computation 
becomes much more voluminous. The Declination 
of the Sun, for instance, must be ascertained to the 
nearest second, both at rising and setting, because 
it is not the same at the two times, except when his 
Right Ascension is about 6 or 18 hours. The lati- 
tude of the place must also be ascertained accu- 
rately. Then, the refractive power of the atmos- 

Define and explain (the figures refer to the sections) : 

137. To find the time of Culmination. 138. Rising and setting ; refraction ; effect of Sun's Declination ; long days 
and short nights ; near the South Pole. 139. Semi-diurnal Arc. 140. Differences. 141. How to apply tabular correc- 
tion. 142. Difference due to Refraction. 143. Refraction for fixed stars ; for the Sun ; rising and setting of Sun's 
upper and lower limb. 144. Right Ascension and Declination from Longitude and Latitude. 145. Examples in Culmi- 
nation ; rising and setting. 146. Greater Exactness. 



phere varies slightly with the height of the barom- 
eter, and the Sun's apparent diameter is not always 
exactly the same, being greatest when he is nearest 
to the earth — about the beginning of January — 
and least when the earth is in the opposite point of 
her orbit (Sec. 12). This book is not intended to 
teach these intricacies ; but it is well that the stu- 
dent should know that accurate astronomical calcu- 
lations involve the use of much time and an exten- 
sive acquaintance with mathematics. 



MAP NO. XIV. 



147 '. This map shows, in diminished size, on a 
circular projection, all the prominent constellations 
visible in the United States. The center is the 
North Pole ; the concentric circles are parallels of 
Declination, the third from the center being the 
Equinoctial ; these parallels are those respectively 
of 30°, 60°, 90°, and 120°, of North Polar distance, 
the inside of the graduated circle representing 135° 
North Polar Distance, or 45° of South Declina- 
tion. The eccentric circle is the Ecliptic, divi- 
ded into twelve signs by as many portions of cir- 
cles ; it crosses the Equinoctial on the radial lines 
of Oh. and 12h, Right Ascension. Each of the 
smaller divisions on the outer circle corresponds to 
1° in Right Ascension, or 4 minutes of time. The 
map shows all the Fixed Stars of not less than the 
third magnitude, with many of the smaller stars. 

148. To find what stars are on the Meridian at 
any given time : Find the Sun's Right Ascension, 
or the Sidereal time, to the nearest minute, from the 
Table (page 12), and add to this the hours and min- 
utes elapsed since the preceding noon, rejecting 24 
hours from the total, if it exceed that amount. 
Look for the sum of the two times, on the outer 
circle of the map, and lay a flat ruler from this 
point across the map, passing through the center. 
The edge of the ruler will show the meridian line 
for the time assumed ; that part of the line between 
the noted point and the center being the meridian 
above the pole ; that portion lying on the other 
side of the center is a part of the meridian below 
the pole. 

149. To find the position of the stars with 
respect to the horizon, at any time, in any latitude 



(North) : From the diagram on the next page set a 
pair of compasses to the size indicated for any re- 
quired latitude : Describe the circle on a piece of 
stiff, transparent paper, draw the meridian line, 
and mark on it the place of the North Pole. Cut 
out this circle, and lay it on the map, the Polar 
point coinciding with the center of the map, and 
the longer side of the meridian line coinciding with 
the upper meridian line found as in Sec. 148. 
The edge of the paper will show the place of the 
horizon ; the straight line the meridian. The stars 
within the circle will be above the horizon ; those 
without the circle will be below the horizon. Turn 
the paper round till the horizon line passes through 
any given star or constellation, and the difference 
of time, as pointed to by the meridian line, will 
show how much earlier or later than the assumed 
time the star, or group, will rise or set on that day. 

150. To find the position of the Prime Vertical, 
or the circle which passes through the Zenith and 
the Eastern and Western Points of the horizon : 
Lay the circle on the map, the polar centers coin- 
ciding. Subtract the latitude from 90°, the remain- 
der is the distance of the Pole from the Zenith. 
Estimate this distance from the Pole along the 
longer side of the meridian line, which can be done 
nearly enough on the 30° intervals. Draw an arc 
of a circle through that point and the two points 
marked " East " and " West " on the diagram. 
That curve will represent the prime vertical. It is 
represented on the diagram, for the latitude of 40°, 
by the curve marked " East" and " West." 

151. The horizon circle may be drawn for any 
latitude between 20° and 60°, with sufficient exact- 



}lavM9XTV 

*' ' XVIII 




POSITION ABOVE THE HOEIZON. 



61 



ness, by estimating for the intermediate position 
of the center, and striking the circle exactly through 
the points of intersection of all the circles in the 
diagram. Or, the circle of the horizon may be 
drawn independently, for any latitude, by finding 
in the table of differences (page 56) the difference 
for 30° or 60° of declination in the given latitude, 



setting off the semi-diurnal arcs from any meridian 
on Map No. XIV., on the Circles of Declination 
(parallels), and finding a point in the meridian from 
which, as a center, the horizon circle may be 
struck, passing through the given points on the 
Declination Parallels, and also crossing the Equi- 
noctial in two exactly opposite points. 




Define and explain (the figures refer to the sections) : 

147. Map No. XIV. ; concentric projection. 148. Stars on the meridian at any given time. 149. Position of Stars 
with reference to the horizon. 150. Prime Vertical. 151. Circle of the horizon. 



THE SOLAR SYSTEM. 



152. Several star-like bodies are often seen in 
the heavens, among the fixed stars already de- 
scribed, but changing their places with varying 
degrees of rapidity ; always, however, within a few 
degrees of the Ecliptic line (Sec. 27). They some- 
times appear to move forward with steady pace, 
increasing their longitudes nightly ; then are sta- 
tionary, keeping the same place among the fixed 
stars for several nights in succession ; then seem to 
move backward among the stars, which is called 
Retrograding ; and after another stationary period, 
again move forward. 

The comparative prominence and brilliancy of 
each of these bodies varies with its rate of move- 
ment, the greater number being most brilliant when 
retrograding ; but they all shine with a steady 
light, and by this peculiarity are easily distinguish- 
able from the fixed stars, which twinkle. Viewed 
through the telescope, the difference is much 
greater ; these bodies have then an appreciable, 
measurable, angular magnitude, while the brightest 
fixed star is but a luminous point. The reason of 
this difference has been ascertained to be, that 
these wandering bodies are comparatively near to 
us, and only shine with a reflected light, whereas 
the fixed stars are luminous bodies ; shining, like 
the Sun, with their own light. 

153. Five of these wanderers are so easily 
recognized, as to have attracted attention in a very 
early age of the world's written history. They are 
named Mercury, Venus, Mars, Jupiter, and Saturn. 
In common with our earth, more than a hundred 
smaller but named bodies, and, possibly, millions 



of others, still smaller and unnamed, they form a 
family called the Solar System. Each named mem- 
ber of the family, and probably every one, rotates 
on an axis of its own, in the same manner as does 
the Earth, and, like her, perforins a circuit around 
the Sun. The time of revolution varies from 
eighty-eight days, in the case of Mercury, to nearly 
165 years, in the case of the most distant known 
member of the family. 

151. Jupiter. — The largest of these is Jupiter, 
a white-colored planet, with a bluish tinge ; at 
times so brilliant that he has been said to cast a 
shadow — which, however, is an exaggeration. 
The table on the next page gives his approximate 
longitude and latitude during the last thirty years 
of the present century, for that time in each year 
when he is on the upper meridian at Solar mid- 
night, and also at the maximum of his brightness 
for the year. 

155. At these times the Earth is in direct line 
between the Sun and Jupiter, and the planet is 
said to be " in Opposition " to the Sun, rising when 
the Sun sets, setting when the Sun rises, and clearly 
visible in the Southeast on a fine evening. At the 
time of Opposition the planet is apparently Retro- 
grading (Sec. 152), and continues to move back- 
ward for sixty days, at which time his longitude 
has decreased about 5° ; that is : sixty days after 
Dec. 13th, 1870, the longitude of Jupiter will be n 
16£°. At the expiration of this time he appears to 
remain stationary among the fixed stars for about 
five days, then commences to move forward to the 
East, preceding the Sun, at first slowly, then more 



APPAEENT MOTION OF JUPITEE. 



63 



rapidly, but losing ground, so to speak, and setting 
a little earlier each evening, his brilliancy also 
gradually diminishing. Six months and a half 
from the time of Opposition, he is no longer visi- 
ble to the naked eye ; he is behind the Sun, and 
is then said to be " in Conjunction." A month 
later the planet is visible in the East just before 
Sunrise, and from then till four and a half months 
after the Conjunction, his distance from the Sun 
and his brilliancy increase, the planet moving for- 
ward among the stars, but so much more slowly 
than the Sun, that he is relatively receding, and 
rises earlier each morning. Then he becomes once 
more stationary for five days, and then retr 



DATE. 

1869 Nov. 8 

1870 Dec. 13 

72 Jan. 15 

73 Feb. 15 

74 March 15 

75 April 15 

76 May 18 

77 June 20 

78 July 25 

79 Aug. 31 
1880 Oct. 7 

81 Nov. 14 

Dec. 18 



84 Ja 



19 



85 Feb. 20 



LON 


GITTTDE 


LATITUDE. 


« 


16 ° 


s. 


1°18' 


ri 


21* 


s. 


29 


S3 


25 


N. 


27 


a 


26 


N. 


1 11 


m 


26 


N. 


1 34 


=A= 


26* 


N. 


1 33 


m 


27 


N. 


1 4 


$ 


29 


N. 


17 


£? 


H 


S. 


39 


X 


8 


S. 


1 25 


°P 


15 


S. 


1 39 


8 


21* 


S. 


1 13 


n 


26* 


S. 


21 


S3 


30 


N. 


34 


m 


1 


N. 


1 16 



through 5°, in 57 to 60 days, when he is again in 
Opposition — on the meridian at midnight. The 
time occupied in this entire revolution, from 
Opposition to Opposition, is a little more than thir- 
teen months, four of which have been occupied by 
the Retrograde movement, and nine by a forward 
motion in the Ecliptic. This is called the Synod- 
ical Revolution. During that time the planet 
has really moved forward a little more than 30° 
among the stars, and the Sun has passed over one 
annual circuit and about 30° more, just as the 
minute hand of a clock passes round the dial more 
than 1^2 times between two successive coinciden- 
ces with the hour hand. 

DATE. LONGITUDE. LATITUDE. 



1886 March 20 


^ 


1 ° 


N. 


1 


5 36' 


87 April 


20 


m 


1 


N. 


1 


30 


88 May 


22 


t 


H 


N. 





58 


89 June 


24 


Y3 


3 


N. 





9 


1890 July 


29 


£7 


7 


S. 





48 


91 Sept. 


5 


X 


13 


S. 


1 


30 


92 Oct. 


13 


T 


20 


s. 


1 


37 


93 Nov. 


18 


« 


26 


s. 


1 


6 


94 Dec. 


22 


S3 


1 


s. 





13 


96 Jan. 


24 


a 


4 


N. 





42 


97 Feb. 


24 


m 


5 


N. 


1 


21 


98 March 25 


=2= 


5 


N. 


1 


37 


99 April 


25 


m 


5 


N. 


1 


27 


1900 May 


26 


# 


6 


N. 





53 


01 June 


29 


Y3 


8 


N. 





1 



156» From the above table the place of Jupiter, 
near the Ecliptic, may be approximately found, 
almost by simple inspection, for any time during 
the remainder of the century. For two months 
before and after the time of opposition, he is with- 
in 5° of the place given in the table for that year, 
and during the other nine months of the thirteen 
he increases his longitude by an average of nearly 
4° per month, or 1° per week. The latitude is 
never greater than that given in the table. 

The Right Ascension and Declination may 
be known from the table on page 58, increasing 



or diminishing for the latitude ; the times of cul- 
minating, rising, and setting may then be ascer- 
tained by the Rules in Sees. 137 and 141 ; or the 
times may be gathered by reference to the nearest 
fixed stars. 

157. The phenomena above referred to are 
explainable only in one way. The Planet Jupiter 
moves around the sun once in about twelve years 
(from any star to the same star again, this being 
called his Sidereal Revolution), in an orbit exterior 
to that of the earth (Sec. 12). If the earth were 
the center of his motion, as was formerly supposed, 



64 



ASTRONOMY. 



the apparent movement would be regularly for- 
ward, as is that of the Sun ; and the two hands 
of a clock (Sec. 155) would represent, also in 
uniformity, the relative motions of the Sun and 
Jupiter. We may, however, use the clock as an 
illustration, by supposing the hour hand to be 
lengthened to a little more than five times the 
length of the minute hand ; Jupiter to be at its 
extremity, and the earth at the point of the min- 
ute hand, while the Sun is on the pivot in the cen- 
ter of the dial, the fixed stars being so remote that 
two lines drawn from any one of them to two 
opposite sides of the dial, would be parallel to each 
other. 

The following diagram shows the relative 
positions at several times during one Synodical 
Revolution : The Arc A J represents the path of 
Jupiter between two conjunctions: B H is the 
space traveled by him in twelve months, divided 
into six equal portions of two months time, or 
about 5° of angular space. The complete circle 
represents the Earth's orbit, divided into six equal 
parts of 60°, each part corresponding to two 
months of her Annual Revolution. The center is 
the place of the Sun. 

If the Earth and Jupiter be at the points marked 
A A, the sun will be in apparent conjunction with 
Jupiter; when, two weeks afterwards, they are at 
B B, the planet will appear to have moved forward 
from A to B, though the Sun will have moved 
over the greater angle measured by V E. Two 
months after the position B B, they will be at C C, 
the Sun being seen beyond F. Two months more 
brings the Earth and Jupiter to D D ; and now the 
combined motion commences to change the direc- 
tion of the line joining their centers, the Earth 
moving so much the more rapidly of the two, and 
the line F F points 10° backward from the direc- 
tion of the line D D. The four months occupied 
in the passage from D to F is the period of Retro- 



gradation ; its middle point is the time of the 
opposition-at E E, the Sun then being seen in the 
direction of B. 




At F F the change of direction of the line ceases 
for a time, and Jupiter appears to be stationary, 



JUPITER AND VENUS 



65 



then to move forward in the direction of the arrows 
as the Earth passes round to J, where Jupiter is 
again seen as in Conjunction with the Sua. Dar- 
in o- the Synodic Revolution, the Earth has passed 
twice over the Arc A B J, equal to one month in 
excess of the twelve occupied by her own revolu- 
tion. The Synodic period of the Earth and Jupi- 
ter is, more exactly, 398,867 days. 

The position of a star, or planetary body, as seen 
from the Earth, is called its Geocentric position. 
The word " Heliocentric," as applied to place or 
motion, signifies that the Sun is assumed as the 
center of observation. 

158. The latitude of Jupiter is accounted for 
by the fact that his orbit is not exactly coincident 
with that of the earth, but makes with it an angle 
of 1° ]8' 42", 4., the two circles crossing each other 
in 9° 21' 27" of the signs S3 and Y3- The lack of 
equality in the yearly Arcs of the planet is due to 
the fact that neither of the two orbits is exactly 
circular (Sec. 16). 

159. Venus. — This planet, of a bright silver 
hue, is even a more prominent object in the hea- 
vens than Jupiter, but not so often visible, from 
the fact that she is never seen more than about 47° 
distant from the Sun, and is often so close to him 
that her brightness is darkened by the greater 
intensity of the solar rays. 

Observation, sufficiently long continued, shows 
that Venus is visible from 45° to 47° East of the 
Sun, at intervals of a little more than nineteen 
months, being then seen in the West, soon after 
Sunset, and called The Evening Star ; from the 
time of this, her greatest elongation East, her dis- 
tance gradually diminishes, till, in about seventy 
days, she is close to the Sun, and has, on two occa- 
sions, been seen to pass across the face of the 
luminary as a dark spot, showing that she is then 
between the Earth and Sun, and that the bright 
side of the planet is towards the Sun. This is 



called her Inferior Conjunction. From this time 
the Sun gradually leaves her behind, till, at the end 
of seventy days more, she is elongated 45° to 47° 
to the West of the Sun, rising before him in the 
East, and hence called The Morning Star. She 
then again approaches the Sun, and in about seven 
months from the time of greatest elongation, she is 
again in Conjunction, but this time the Sun is 
between the Earth and Venus ; hence this is called 
her Superior Conjunction. The planet is now 
moving at the rate of 1° 15' daily, and gaining on 
the Sun 0° 15' per day, a progress which soon car- 
ries her Eastward of the Sun into the position of 
Evening Star; she attains her greatest elonga- 
tion in seven months from the time of the Supe- 
rior Conjunction. 

160. There is but one theory which enables us 
satisfactorily to account for these phenomena ; it 
is, that Venus revolves around the Sun in an orbit 
within that of the Earth. The diagram on the 
next page shows the relative positions as above 
noted. The outer circle represents the Earth's 
orbit ; the next to it is the orbit of Venus. 

When the Earth and Venus are at A A, Venus 
is advancing directly towards the Earth, and there- 
fore is not changing her apparent place among the 
fixed stars ; this is the position at the time of her 
greatest Eastern Elongation, her apparent distance 
from the Sun being equal to the angle A" A' S. 
She is now the Evening Star. Fifty days after- 
wards, the Earth and Venus are at BB; this is 
the beginning o"f retrogradation (Sec. 152). Twen- 
ty-one days still later, they are at C C, and Venus 
is then in her Inferior Conjunction. At D D the 
retrograde motion ceases, and at E E the planet is 
at her greatest Western elongation. During the 
next seven months, while they are passing round to 
the position F F, Venus rises before the Sun, and 
is the Morning Star. At F F, she is in Superior 
Conjunction, and thence, for nine and a half 



ASTEOyOMT 



months, till the position I I is reached, she is Eve- 
ning Star — retrograding during the passage from 
HtoK. 




From the time of the Inferior Conjunction at 
C C to the one at I I, is a little more than one year 
and seven months ; during that time the Earth has 



performed one revolution and seven-twelfths of 
another, and Venus has passed twice round her 
orbit, and described seven-twelfths of a third cir- 
cuit. The mean time of the Synodical revolution 
is 583.92 days; the time of Venus' Sidereal revo- 
lution — as from C to C again — is 224f days. 

161. Venus is so much nearer to the Earth at 
the time of Inferior Conjunction than when they 
are on opposite sides of the Sun, that she -would be 
about forty-five times brighter if she were equally 
luminous on all parts of her surface. But shining 
only with light received from the Sun on that side 
which is turned towards him, her apparent bright- 
ness does not materially vary, as near the time of 
her Inferior Conjunction her dark side is partially 
presented to us. 

162. The following table shows the date and 
the longitude of Venus at the time of each Infe- 
rior Conjunction during the last thirty years of the 
present century. Her approximate jJosition at any 
other time, may easily be found by allowing a pro- 
portionate distance, East or "West. She retro- 

| grades 8°, during 21 days, on each side of the Infe- 
I rior Conjunction : 



DATE. 




longitude. 


DATE. 




LOXGITTOE. 


DATE. 




LONGITUDE 


370 Feb. 


23 


X 


H° 


1881 May 


1 


8 


ii ° 


1892 July 


5 


S3 I5£° 


71 Sept. 


26 


^ 


2F 


82 Dec. 


6 


$ 


16 ° 


94 Feb. 


14 


£} 27f° 


73 May 


4 


8 


1H° 


84 July 


8 


S3 


17f° 


95 Sept. 


17 


m 25^° 


74 Dec. 


9 


t 


isi 3 


S6 Feb. 


17 


£7 


30 ° 


97 April 


25 


8 6 ° 


76 July 


11 


S3 


20 ° 


87 Sept. 


20 


m 


28 ° ' 


98 Nov. 


30 


$ m° 


78 Feb. 


20 


y: 


9J_o 


89 April 


28 


8 


sv 


1900 July 


2 


S3 13£° 


79 Sept. 


23 


=*= 


o|° 


90 Dec. 


3 


t 


13f° 









163. Venus will cross the face of the Sun at the 
time of Inferior Conjunction, twice only during 
this period — in 1874 and 18S2. At the other Con- 
junctions she will be North or South of the Sun, 
because the plane of her orbit does not exactly 
coincide with that of the Earth, but makes with it 
an angle of 3° 23' 32", cutting it in 15° 33' 6' of n 
and $ . While passing in her orbit from n to $ , 



her latitude is North, and from f to n it is South. 
When Venus is in Superior Conjunction, her 
apparent Latitude is of the same name as the Real 
Latitude, but less in amount, she being then much 
further from the Earth than from the center of her 
orbit at S. But at the Inferior Conjunction she 
is seen in the opposite sign to that occupied by her 
in reference to the Sun. Hence in February, 1870, 



VENUS AND MEECUEY. 



67 



being then more than 60° distant from the nodes, 
or points of intersection, her latitude in the orbit 
will be a little more than 3°, but it will be North 
latitude, she being then in Tl£ as seen from the Sun. 
Her apparent latitude will also be much greater 
than the true — about 8£° — as, being nearer the 
Earth than to the Sun, her actual departure from 
the Ecliptic will be seen under a much greater 
angle than that subtended at the Sun ; the dis- 
tance C C is much less in the diagram than C" 
toS. 

If L, in the preceding diagram, represent the 
position of the Ecliptic plane opposite C", then 
C" L will be the actual distance of Venus from the 
Ecliptic line, and the angle at S will be the latitude 
in her orbit, while the angle at C will be the mea- 
sure of her latitude as seen from the Earth — hence 
called the Geocentric Latitude, or the apparent 
latitude as seen from the Earth as a center. 

161. Mercury. — A dazzling bright speck of 
light, much smaller than Venus or Jupiter, is often 



visible in the East just before Sunrise, for a few | century : 



days, and two months afterwards is seen in the 
West for three or four successive evenings, just 
after Sunset. This is the planet Mercury ; he 
makes an apparent swing, backwards and forwards 
across the place of the Sun, like a majestic pendu- 
lum, six of whose ticks nearly measure one of our 
Earth years. He is never seen more that 28° 20' 
from the Sun, and this distance alternates with 
about 16° as the limit of his greatest elongation on 
each side of the central luminary. 

The inner circle of the preceding diagram repre- 
sents the orbit of Mercury as relative to those of 
the Earth and Venus, except that his path is very 
far from being a perfect circle, he being much 
nearer to the Sun when in the middle of the sign 
H than when in any other part of his orbit. A 
Sidereal revolution around the Sun, once in a little 
less than 88 days, gives a Synodical revolution of 
115,877 days — nearly four months. The follow- 
ing are the approximate times of his Inferior Con- 
junctions during the last thirty years of the present 



1869 June 


24 


1875 Oct. 


29 


1882 Feb. 


22 


1888 July 


9 


*Nov. 11 


Oct. 


20 


1876 Feb. 


12 


June 


28 


Nov. 


1 


1895 Feb. 23 


1870 Feb. 


2 


June 


16 


Oct. 


23 


1889 Feb. 


15 


July 1 


June 


4 


Oct. 


13 


1883 Feb. 


6 


June 


19 


Oct. 26 


Oct. 


3 


1877 Jan. 


27 


June 


7 


Oct. 


16 


1896 Feb. 9 


1871 Jan. 


17 


May 


27 


Oct. 


6 


1890 Jan. 


30 


June 10 


May 


14 


Sept. 


27 


1884 Jan. 


20 


May 


30 


Oct. 9 


Sept. 


17 


1878 Jan. 


11 


May 


17 


Sept. 


30 


1897 Jan. 23 


1872 Jan. 


1 


*May 


6 


Sept. 


20 


1891 Jan. 


14 


May 20 


April 


25 


Sept. 


9 


1885 Jan. 


4 


*May 


9 


Sept. 23 


Aug. 


31 


Dec. 


25 


April 


28 


Sept. 


12 


1898 Jan. 7 


Dec. 


16 


1879 April 


16 


Sept. 


3 


Dec. 


28 


May 1 


1873 April 


6 


Aug. 


23 


Dec. 


19 


1892 April 


19 


Sept. 6 


Aug. 


13 


Dec. 


10 


1886 April 


9 


Aug. 


26 


Dec. 22 


Dec. 


1 


1880 March 


29 


Aug. 


16 


Dec. 


13 


1899 April 12 


1874 March 


18 


Aug. 


5 


Dec. 


4 


1893 April 


1 


Aug. 19 


July 


25 


Nov. 


24 


1887 March 


21 


Aug. 


8 


Dec. 7 


Nov. 


14 


1881 March 


11 


July 


28 


Nov. 


27 


1900 March 24 


1875 March 


1 


July 


17 


Nov. 


17 


1894 March 14 


Julv 31 


July 


6 


*Nov. 


8 


1888 March 


3 


July 


20 


Nov. 20 



165. Mercury is retrograding, like Venus, at | during 11 or 12 days before and after, over an Arc 
the time of Inferior Conjunction, and retrogrades ' of 4° or 5° on each side of the Conjunction. He 



ASTEO^OMY. 



attains his greatest Eastern elongation about 30 
days before the Inferior Conjunction, and is then 
seen as an Evening Star ; his greatest Western 
elongation is about 30 clays after the Conjunction ; 
he is then seen as a Morning Star. His Superior 
Conjunction is about equidistant in time between 
those of Elongation. The orbit of Mercury makes 
an angle of 7° 0' 20' with the Ecliptic, cutting it in 
16° 50' 39* of 8 and TTX. Hence the planet is gen- 
erally North or South of the Sun at the time of 
Conjunction. He is not, however, seen from the 
Earth at any time with so great latitude as 7°, as, 
being much further from the Earth than from the 
center of the orbit, his actual departure from the 
plane of the Earth's motion is seenunder a smaller 
angle than that subtended at the Sun (Sec. 163). 
He will cross the solar body, like a dark spot on 
the surface, at the four times marked with an * in 



the accompanying table. Mercury is the nearest 
to the Sun of any planetary body yet known. 

166. Mars. — This planet is of a ruddy, spark- 
ling hue, and very variable in his apparent size. 
His bright side is always turned, more or less, 
towards us, showing that he is never between the 
Earth and Sun (Sec. 161), while the great variation 
in his apparent magnitude shows that he is com- 
paratively very near the Earth at the time of Oppo- 
sition, and relatively far removed at the time of 
Conjunction. These conditions are satisfied by 
the theory that Mars revolves around the Sun in 
an orbit exterior to that of the Earth, but very 
much nearer than Jupiter. The following table 
shows the longitude and latitude of the planet, 
with the date, at each Solar Opposition during the 
last 30 years of the present century : 



1869 Feb. 13 

71 March 18 

73 April 26 

75 June 18 

77 Sept. 2 

79 Nov. 11 

81 Dec. 27 

84 Feb. 1 



a 25 ° 
TIE 29^° 



a 12 ' 



x. 



3f° 
l|° 

3 fo 

o±° 

4° 





DATE. 




1886 


March 


Y 


88 


April 


11 


90 


May 


27 


92 


Aug. 


3 


94 


Oct. 


20 


96 


Dec. 


11 


99 


Jan. 


19 


1901 


Feb. 


21 



m 



x. 



H° 
H° 

6f° 
2i° 

4 i° 



167. Mars retrogrades through 5° to 10°, in 30 
to 40 days before, and the same after, the Opposi- 
tion, and is apparently stationary during two or 
three days before and after retrogradation. He is 
in Conjunction with the Sun about midway between 
the times given in the above table. His place at 
any other time may be found sufficiently near for 
purposes of general observation by remembering 
that, including the space lost in retrograding, Mars 
goes once round the heavens, and abont 35° more, 
in the year and 11 months between his two sta- 
tionary periods — or an average of about 17° per 
month. 



Tracing him round the heavens in the same way 
as indicated in the case of Venus and Jupiter, we 
find that Mars moves in an orbit whose average 
diameter is 1|- times that of the earth ; his Synodi- 
cal revolution of 779.936 days resulting from a 
Sidereal revolution of 686.979 days, or nearly two 
years. His orbit is inclined only 1° 51' 6" to the 
plane of the Ecliptic, cutting it in 18° 33' 16" of tf 
and TTX, but he is sometimes seen with much greater 
apparent latitude when near the Opposition ; he is 
then much nearer to the Earth than to the Sun, 
and his actual distance from the Ecliptic is there- 
fore seen under a greater angle (Sec. 163). His 



SATURN, AND URANUS 



greatest observed North Latitude is 4° 31' ; the 
maximum of his South Latitude is 6°47' ; the dif- 
ference is due to the fact that the relative eccentri- 
city of his orbit brings him much nearer to the 
Earth when he is South of the Ecliptic, than is pos- 
sible in the Northern half of his circuit. 

108. Satukn. — This planet is of a pale, ashen 
color ; he is not so prominent an object as either 
of those previously noted, though easily recog- 
nized. His motion among the fixed stars is com- 
paratively regular, and so slow that his position 
changes but little for several days in succession. 
He makes a Synodical Revolution in 378.09 days, 
in which time he has moved forward but about 12°, 
making the Sidereal circuit in 10,759.22 days, or 



about 29|- years. He retrogrades 3^° during about 
75 days before, and the same after, the time of the 
Opposition, and is stationary five days before and 
after Retrogradation. 

The orbit of Saturn is exterior to that of Jupiter, 
the diagram for which will answer in the case of 
Saturn, by noting that the Earth is relatively but 
about half as far from the Sun as in the case of 
Jupiter. His greatest observed latitude is 2° 59'. 
His orbit makes an angle of 2° 29' 24" with the 
plane of the Ecliptic, cutting it in 22° 3-4-37* of S3 
and Y3. The following are the longitudes and lat- 
itudes of Saturn at the time of each Opposition 
during the last 30 years of the present century : 



869 June 


4 


t 


14 ° 


N. 


1°47' 


1885 


Dec. 


25 


S3 


4f° 


S. 


70 " 


16 




25 ° 


N. 


1° 20' 


87 


Jan. 


8 




18f° 


S. 


71 " 


27 


V3 


6f° 


N. 


0° 50' 


88 


" 


21 


a 


3 ° 


N. 


72 July 


9 




18 ° 


N. 


0° 18' 


89 


Feb. 


4 




16f° 


N. 


73 " 


21 




29|° 


S. 


0° 16' 


90 


" 


18 


M 


or 


N. 


74 Aug. 


2 


AW 


11 ° 


S. 


0° 49' 


91 


March 3 




13f° 


N. 


75 " 


14 




22f° 


s. 


1° 20' 


92 


" 


16 




26f° 


N. 


76 " 


27 


X 


4f° 


s. 


1° 49' 


93 


" 


29 


=2= 


H° 


N. 


77 Sept. 


8 




16f° 


s. 


2° 13' 


94 


April 


11 




21f° 


N. 


78 " 


22 




29^° 


s. 


2° 32' 


95 


" 


22 


m 


4 ° 


N. 


79 Oct. 


4 


cp 


12 ° 


s. 


2° 44' 


96 


May 


5 




15f° 


N. 


80 " 


18 




25i° 


s. 


2° 48' 


97 


" 


17 




27|° 


N. 


81 " 


31 


8 


8f° 


s. 


2° 43' 


98 


" 


29 


$ 


9 ° 


N. 


82 Nov. 


17 




24|° 


s. 


2° 28' 


99 


June 


10 




20^° 


N. 


83 " 


27 


n 


6i° 


s. 


2° 5' 


1900 


" 


22 


vs 


If 


N. 


84 Dec. 


11 




20^° 


s. 


1° 33' 


1901 


July 


4 




13 ° 


N. 



169. Uranus. — This planet is barely visible 
to the naked eye as a pale, bluish, star-like body, 
of the 6ih magnitude. He is called, also, " Her- 
schel," from the name of his discoverer, and 
" The Georgium Sidus," from the fact that he 
was discovered in the reign of George III. of Eng- 
land. Uranus is still more remote than 'Saturn, 
and changes his place among the stars much more 
slowly. His sidereal Revolution occupies 30,686.- 
821 days, or about 84 years and six days ; his 



0° 32' 

Synodic Revolution is performed in 369.656 days, 
during which time he progresses but 4^° in longi- 
tude. He retrogrades 73 days, through about 2°, 
on each side of the Opposition. His orbit makes 
an angle of 0°46'30" with the plane of the Ecliptic, 
cutting it in 13° 17' 9" of n and } . The follow- 
ing are the longitudes and latitudes at every fifth 
Opposition during the last 30 years of the present 
century. The place and date for intermediate 
years may be easily found by interpolation ; 



70 



ASTEONOMY. 



DATE. 

1870 Jan. 10 
75 Feb. 2 
80 Feb. 24 
85 March 20 



or 



0° 



N. 

N. Of 

N. Of 

N. Of 



1890 April 14 

95 May 8 

1900 May 31 



N. 4 
N. Oi 



170. Neptune. — This is the farthest removed 
from the Sun of any of the known planetary fam- 
ily, and is discernible only by telescopic aid. His 
Sidereal Revolution occupies 60,126.722 days, or 
164 years and 7 months ; his Synodical Revolution 
is 367. 4S8 days, during which time he moves for- 
ward but about 2° in the Zodiac. He retrogrades 
1°22' during 78 days, before and after the time of 



1870 April 10 
75 April 22 
80 May 3 



T 20° 



1885 May 
90 May 



171» The position of a planet among the stars 
at any time, may be readily found by the aid of 
the preceding tables, and reference to the maps in 
this book. Maps Nos. III. to X ., inclusive, show 
the principal stars in all the Zodiacal constellations. 
The Ecliptic, near which the planets are always to 
be found, is divided on those maps into equal 
lengths of 15°, by circles of Latitude, and the posi- 
tion for intermediate degrees may be seen by in- 



Opposition. His orbit makes an angle with the 
plane of the Ecliptic of 1° 47' 2", crossing it in 
11° 9' 30" of Si and £?. Neptune was discovered 
in 1846. The following is his longitude at each 
fifth Opposition from 1870 to the end of the cen- 
tury. His place for any intermediate Opposition 
may be easily found by interpolation : 



1895 June 7 
1900 June 19 



spection. Thus: On November 8th, 1869, the 
planet Jupiter is in opposition to the Sun, in 8 
16°, and on December 13th, 1870, he is in opposi- 
tion, in n 2l£. A reference to Map No. IV. will 
show that the first named position is near d Arietis, 
and the second near Z Tauri; the intermediate 
course of Jupiter may be traced among the fixed 
stars on Map No. IV., by reference to Sec. 156. 



Define and explain (the figures refer to the sections) : 

152. The Solar System ; peculiarity of planetary appearance and motion - y Retrograding ; time of greatest brilliancy. 
153. Planets known to the Ancients ; the Solar family. 154. Jupiter ; places at time of opposition. 155. Phenomena 
of opposition ; retrograding; stationary; in Conjunction; Synodical Revolution. 156. Place of Jupiter at any time. 
157. Motion round the Sun ; Sidereal Revolution ; exterior orbit ; Synodic period. 158. Latitude. 159. Venus ; 
greatest distance from the Sun ; intervals of elongation ; Morning and Evening Star ; Inferior and Superior Conjunc- 
tions. 1G0. Inferior orbit. 161. Venus not self-luminous. 162. Times of her Inferior Conjunctions. 163. Transits of 
Venus; her Latitude. 164. Mercury ; phenomena of elongation ; Revolutions ; Inferior Conjunctions. 165. Times of 
Retrograding and direct motion; inclination of orbit. 166. Mars; phenomena; how accounted for; dates of Solar 
Opposition. 167. Mars' latitude in the orbit. 168. Saturn, phenomena; slow motion, and causes; oppositions for 30 
years. 169. Uranus. 170. Neptune. 171. Place of a Planet among the Fixed Stars. 



THE MOON. 



172. If we watch the course of the Moon for a 
few evenings, we find that she changes her place 
among the fixed stars much more rapidly than the 
Sun, or either of the planets, coming to the meri- 
dian nearly an hour later each day than on the 
day preceding : never retrograde, but w'.th a very 
variable motion. Her period of describing the cir- 
cuit of the heavens, or the time elapsing between 
two consecutive conjunctions with any fixed star, is 
easily found to be something more than 27 days ; 
and from a mean of many hundred revolutions, it 
has been ascertained that her Sidereal Period is 
27d. 11a. 43m. 5s. 

The mean daily motion of the moon is therefore 
13°10'36", but a little observation enables us to see 
that her daily rate of movement is continually 
changing, it being sometimes less than 12°, at 
others more than 15°, in longitude. We also find, by 
comparison of anciently recorded observations with 
those of recent date, that the period of her revolu- 
tion is slowly diminishing. During the time of her 
Sidereal Revolution, the Sun has progressed about 
27° in longitude, and moves over about 2° more 
while she is passing that additional space. The 
Moon thus travels about 389° between any two 
consecutive Conjunctions — New Moons — in 
29.53059 days. This, the Synodic Revolution, is 
also called a Lunation. Hence the Moon describes 
twelve complete Lunations in 11 days less than a 
year. 

173. The Lunation. — That the Moon revolves 
around the Earth as the center of her motion, is 
evident from the fact that, unlike the planetary 
bodies (Sec. 152), she is never Retrograde. That 



she is not self-luminous, but receives her light from 
the Sun, is shown by the different phases she 
assumes, according to her position with respect to 
him. 

The diagram on the next page will convey an idea 
of the principal phenomena of the Lunar motion. 
The inner circle represents the Earth ; the outer 
circle is the Moon's orbit, or its projection on the 
plane of the Ecliptic. The Sun is supposed to be 
outside the limits of the drawing, his center in the 
direction of the line C S, beyond S ; the other lines, 
running nearly in the same direction as C S, are 
supposed to be drawn to the outer edges of the 
Solar body or disc. 

When the Moon is between the Earth and Sun, 
her illuminated side is turned directly from us ; we 
see only a dark mass ; she is then called " The 
New Moon." From this position she gradually 
increases in light, till at a distance of 90° in longi- 
tude, when we see one half of her Western, or illu- 
minated surface, she then being East of the Sun, 
and setting after him - % she is then in her First 
Quarter. As her angular distance from the Sun 
increases, we see more and more of her enlight- 
ened surface till she arrives at the " Full," when, 
being in Opposition, her illuminated side is turned 
directly towards us. From this, to the time of 
New Moon, her light, diminishes, presenting the 
same changes, but in inverse order, till she be- 
comes again totally obscured at her Conjunction 
with the Sun. 

That the Moon is an opaque body is evident, 
from the fact that when passing directly between 
us and the Sun, or a star, she hides them com- 



ASTRONOMY 



pletely from our view, producing, in the one case, 
an Eclipse ; in the other, an Occultation. 




174:. Latitude. — The Moon is seldom found 
on the Ecliptic. Her orbit makes an angle of 
5° 8' 48", with the plane of the Sun's apparent path. 
The point where she crosses the Ecliptic into North 
Latitude is called the North Node, the place 
where she changes from North to South Latitude 
is the South Node. The places of the Lunar Nodes 
are constantly retrograding, making the circuit of 
the Ecliptic in about 18 years and 124 days, in 
consequence of which she performs her revolution 
from Node round to the same Node again, in 
about 27 days 5 hours ; or in 2f hours less than 
the time of her Sidereal Revolution. 



175. The Moon rotates on her own axis, but it 
has been found that her period of rotation is co- 
incident with that of her Sidereal Revolu- 
tion, so that she always presents the same 
side to us. Nevertheless, we see, at dif- 
ferent times, much more than half of her sur- 
face ; when she has great South Latitude 
her Northern side is more fully turned 
towards us, and vice versa. This bal- 
ancing over, or vacillation, is called her 
Libration in Latitude. She has, also, a 
Libration in Longitude, her motion in her 
orbit being variable, while the rotation is 
uniform. 

17G. Eclipses. — When the centers of 
the Sun, Earth, and Moon are in one straight 
line, the light of one of the Luminaries is 
obscured for a time, and it is said to be 
Eclipsed. If this occur at the time of Full 
Moon, the lunar light is obscured during 
her passage through the Earth's shadow ; 
if at the time of New Moon, the light of 
the Sun is prevented from reaching us by 
the interposition of the Moon, whose dark 
side is then turned towards us. 

If the Moon's orbit coincided with the 
Ecliptic there would be an eclipse of the 
Moon at every Full, and an eclipse of the Sun 
at every New Moon. But her orbit being inclined 
to that of the Earth (Sec. 174), an Eclipse can 
only occur when, at the time of New or Full, the 
Moon is also in, or near, her Nodes ; at all other 
times she will pass so far above or below the line 
B S as neither to suffer or cause privation of light. 
The greatest distances from the Nodes at which 
the Eclipse can possibly occur, are called the 
" Moon's Ecliptic Limits." In order to calculate 
these it is necessary to find, by observation, the 
angular magnitudes of the Earth, Sun, and Moon, 
as seen from each other. 



THE MOON ECLIPSES. 



73 



177. Parallax. — The word means "change 
of place." A line from the Earth's center to the 
edge of the Sun's disc, nearly coinciding with the 
line C H, will make a small angle, at A, with the 
line A S, joining the centers of the Earth and Sun. 
This angle is the measure of the Sun's Semidia- 
meter ; it varies from about 0° 16' 18.2", in the be- 
ginning of January, to 0" 15' 46" in the beginning 
of July. The small angle formed at the Sun's 
center, by lines drawn from A and P, is the angular 
value of the Earth's Semidiameter, as seen from 
the Sun; it is about 8"95 — less than 9 seconds of 
Arc — and is called the Sim's Horizontal Par- 
allax, it being the difference in the position of 
the Sun among the fixed stars, as seen at the same 
instant of time in the zenith of one observer, and 
on the horizon of another. 

The Semidiameter of the Moon, as seen from 
the Earth's center, varies from 0° 16' 46" to 0° 14' 
44". The angle subtended by the Earth's Equa- 
torial Semidiameter, as seen from the Moon, is 
called " The Moon's Horizontal Parallax," being 
the angular difference of position of the Moon 
among the fixed stars, as seen at the same instant 
in the zenith of one observer, and on the horizon 
of another. This angle is about 1° 1' 25" at the 
Equator, when the Moon's apparent Semidiameter is 
greatest, and both diminish in the same proportion. 

The change in the magnitude of these angles is 
evidently caused by a change in the actual dis- 
tance between the respective bodies, as an object 
half a mile distant from the eye of the observer 
appears to be twice as large as if seen at the dis- 
tance of one mile. 

When the Moon is at her greatest distance from 
the Earth — her angular magnitude being least — 
she is said to be in Apogee ; when at her least dis- 
tance, she is said to be in Perigee. Similarly : the 
Earth's greatest distance from the Sun is called 
her Aphelion ; her least distance is the Perihelion. 



178. The Moon's angular magnitude may be 
measured very nearly by the aid of a simple appa- 
ratus. If we so fix a narrow board as that its 
flat surface will be turned towards the Full Moon, 
and move backwards or forwards till the Moon is 
apparently just shut out by the board from the 
view of one eye, the distance of the eye from that 
part of the board which is in a direct line with 
the Moon will be the radius of a circle, which, mul- 
tiplied into 3.14159, and the product divided by 
180, will give the measure of one degree to that 
radius (Sec. 22). Then half the width of the 
board, divided by one sixtieth part of the last 
found quantity, will give the number of minutes 
of space in the Moon's Semidiameter at the time 
and place of observation. 

The Sun may be measured in the same way, by 
using a piece of smoked glass to prevent the eye 
from being dazzled by his rays. The method of 
finding the parallax is explained subsequently (See 
Sees. 194 and 197). 

179. Lunar Eclipses. — Let E A P, in the 
diagram, represent the horizon of the earth, and the 
base of her conical shadow, projected far beyond 
the Moon's orbit ; F B D is a circular section of 
the shadow, at the distance of the Moon ; A B, 
the distance of the centers of the Earth and Moon 
at the time of Full — the line A B being a contin- 
uation of that joining the centers of the Earth and 
Sun. We have given the angle ABE — equal to 
the Moon's Parallax, — and the angle made by the 
line E D with A B — equal to the Sun's Semidi- 
ameter diminished by his Parallax — to find F A B, 
or the angular Semidiameter of the shadow on the 
lunar orbit, The angle E B A, diminished by the 
angle formed by A B with E D, is equal to B E D. 
That is : Moon's Horizontal Parallax, minus Sun's 
Semidiameter, plus Sun's Parallax, equals DEB 
or B A F. This sum must, however, be increased 
by about one sixtieth part, for the refraction of the 



74 



ASTRONOMY. 



Sun's rays in passing through our atmosphere. 
Let now X B represent a part of the Ecliptic ; 
X, the place of the Moon's Node ; and X N, a por- 
tion of her orbit ; then, if at the time of Full, the 
edge — or limb — of the Moon, just touch the 
shadow without being obscured ; it is evident that 
the latitude — B N — of the Moon's center, will be 
equal to the sum of the Semidiameters of the Moon 
and shadow. By Spherical Trigonometry, Tan- 
gent of B 1ST, into Cotangent of X, equals Sine of 
B X — the distance from the Node beyond which 
an eclipse can not occur. B N is manifestly great- 
est when the Earth is in Aphelion, and the Moon 
in Perigee. That is : 



Moon's Greatest Parallax 
Sun's least Semidiameter - 
Sun's Parallax 



+ 1° 1'25 ; 

. _o°]5'46 ' 

+ 0° 0' 8£' 



Greatest Semidiameter of Shadow - 0°45'47 
Increase by one sixtieth part - 45 

Moon's greatest Semidiameter - - 0°16'46 



Maximum of B N - 



BN=1°3'19"; Log Tan - 
Angle X=5°8 48" ; Log Cot - 



B X=ll°48; Log Sine 



9,310,720 



The angle at X is sometimes a little less than 
5°8 48" ; hence the limit of Lunar Eclipses is 
extended to about 12° in longitude from the Node. 
If the Moon be in her Node without Latitude, as 
at B, the shadow being so much larger than the 
Lunar disc, the Eclipse is total, and of considera- 
ble duration. 

If the distances of the luminaries be as above, 
the difference of diameters of Moon and shadow is 
0°59 34", a space over which the Moon will pass in 
about lh. 55m.: and for some time before and 
after this, a portion of the Moon's disc will be 
obscured, while she is entering and leaving the 
shadow. If the Moon be not in her Node, yet if 



the difference of Semidiameters be greater than 
her latitude, the Eclipse will be total, but not of so 
long duration ; if the latitude be greater than the 
difference, the Eclipse will be but partial. 

Besides this shadow proper — the Umbra — there 
is another — the Penumbra — external to the first, 
and surrounding it ; the limit of this — E K — is 
determined by a line drawn from the opposite edge 
of the Solar disc ; its Semidiameter is evidently 
equal to that of the Umbra, plus the Sun's diame- 
ter; it is not so dark as the Umbra. 

An Eclipse of the Moon appears the same to all 
parts of the Earth's darkened hemisphere, because 
the Moon is really deprived of light while passing 
through the Umbra. She has usually a faint, dull 
hue, somewhat resembling that of tarnished copper 
— an appearance probably due to the Solar light 
refracted by the Earth's atmosphere. 

180. Solar Eclipses. — Eclipses of the Sun 
occur only at the time of New Moon. In the dia- 
gram — having given the same quantities as for 
the Lunar Eclipse — the angle H C S will be the 
Sun's apparent Semidiameter ; let M represent the 
center of the Moon. It is evident that the dis- 
tance L M will be the limit of latitude of a Solar 
Eclipse, when the line K E II is a tangent to the 
surface of the Moon at M. When, therefore, the 
angular values are the greatest possible, we have : 

L R=Sun's greatest Semidiameter - C^lG'lS" 
RM=Moon's " " +0°16'46" 

E R A=Moon's greatest Parallax - +1° 1'25" 
A H E= Sun's Parallax - - - +0° 0' 8" 
For Refraction of Moon's atmosphere add 3" 

L M=Latitude Moon's Center - 



1°34'40" 



LM=1°34'40"; Log Tan - - 8,440.027 

Inclination =5°8'48"; Log Cot - - 11,045.427 

Limit=l7°48f. Sine - - - 9,4S5.454 

The angle being sometimes a little less than 

5°8'48" we assume 18° to be the limit of Solar 



ss. 



75 



Eclipses in longitude from the Node. If we now 
regard LMasa difference in longitude, we shall find 
that the Moon passes over the distance in 2h. 30m., 
nearly, which, doubled, gives 5 hours for the time 
of passage of the apex of the Umbra from E to P, 
— from the Western to the Eastern edge of the 
Earth's disc — when the Moon is in her Node. If 
the Moon be not on the Ecliptic, but still within 
limits, the shadow passes over a smaller portion of 
the Earth's surface, and the time of passage is less- 
ened ; if her latitude exceed the sum of the above 
quantities, her shadow passes Northward or South- 
ward of the Earth, and the Sun is not eclipsed. 

181. When the Earth is in Perihelion, and the 
Moon in Apogee (Sec. 177), the Sun's apparent semi- 
diameter is 0°1'34" larger than that of the Moon 
(16'18" — 14'44"). If at that time the Moon's cen- 
ter be in a line with that of the Sun and the eye 
of the spectator, the dark body of the Moon is 
seen surrounded by a ring of light, the breadth of 
which is equal to the difference of the Semidia- 
meters. This is called an Annular Eclipse — the 
apex of the shadow does not extend to the Earth's 
surface. 

When the Earth is in Aphelion, and the Moon in 
Perigee, the Moon's Semidiameter is greatest by 
0°1'0" only. The period of total darkness at any 
place can not, therefore, exceed the time required 
for the Moon to traverse that distance ; the maxi- 
mum time is 3m. 13s., but this is increased to the 
extent of a few seconds by the rotation of the 
Earth on her axis in the same direction. The 
mean rate of motion of the shadow over the Earth's 
surface is about 1,830 geographical miles per hour, 
or 30|- miles per minute. 

The radius of the shadow at the Earth's surface 
will be nearly to the Earth's Radius, as the Tan- 
gent of the difference of Semidiameters is to the 
tangent of the Moon's Parallax. The Earth's 
radius being 3,962f miles (Sec. 5), the radius of 



the shadow in the last ease will be 64.7 miles. 
This is, approximatively, the half breadth of a zone, 
to every portion of which the Eclipse will be total. 
When exactness is required, a separate calculation 
must be instituted for every place from which it is 
wished to view the eclipse, as the variation of the 
Moon's Parallax during the time of Eclipse is often 
so great as to make a considerable difference in the 
result. 

When the Sun and Moon are both at their mean 
distances from the Earth, the Lunar shadow just 
reaches the surface, and the space to which the 
Eclipse is total is reduced to a mathematical line. 

182. The angular value — R — of the Penum- 
bra — E R C — is equal to the sum of the semi- 
diameters of the luminaries. Making L A radius, 
we have, L A into tangent of lunar parallax, equals 
A E, the Earth's radius. Similarly, L A into tan- 
gent of the penumbral angle, equals the semidia- 
meter of the Penumbra at the Earth. That is, in 
the last case, the Penumbral limit is the Arc C V, 
or 31°58f , equal to 0.5296 when the radius is 1. 
If the line of Central Eclipse be in the Zenith, as 
at C, this proportion gives the sine of the semi- 
spherical surface covered by the Penumbra, but in 
any other position — as ME — it expresses the 
perpendicular distance, in parts of the Earth's 
radius, of the limit from the axis of the Cone — as 
W Y. 

The Sun is partially eclipsed at all places inclu- 
ded in the Penumbra, but the times and phases 
are different for each place, as the apparent posi- 
tion of the Moon, with regard to the Sun, depends 
on her parallactic angl.e, which varies widely, at 
times, in places only a few miles distant. 

In Solar Eclipses, the Moon's dark surface is 
usually marked by a faint light, which is probably 
due to reflection from the Earth's atmosphere ; 
during the total Eclipse she is surrounded by a 
pale circlet, which has been attributed to the Sun's 



76 



A S TE ONOIY. 



atmosphere, but is more probably due to a com- 
paratively small lunar atmosphere. 

183. The number of Eclipses in any year can 
not be less lhan two, nor greater than seven ; the 
most usual number is four, and there are seldom 
more than six. It" there be seven, five will be of 
the Sun ; if only two, both must be Solar. There 
can never be more than three Lunar eclipses, and 
may be none at all The reason of this is, that the 
Sun passes both Nodes but once in a year, unless 
he should pass one of them in the first few days of 
the year, in which case he will pass it again a few 
days before the year is finished, because the Nodes 
move backward (Sec. 174) about 19+° each twelve 
months, and the Sun passes from one to the other 
in about 173 days; if either Node be in advance 
of the Sun about 15° at the New Moon, he will be 
eclipsed, and at the subsequent Full the Moon will 
be eclipsed near the other Node, and will come 
round to the Sun's Conjunction, eclipsing him 
again about 15° from the Node ; the same number 
may occur six months afterwards, near the other 
Node; when six more lunations are completed, and 
the Sun arrives again at the first Node, the year 
will lack but a day or two of being ended, and the 
Sun will be again eclipsed. 

There may thus be three eclipses about each 
Node — two of the Sun, and one of the Moon — 
but if the Moon change close to either Node, she 
will be beyond the limits — 12° — at the preceding 
and succeeding Full, and in six months more she 
will change near the other Node, under the same 
circumstances, in which case there will be but one 
eclipse — of the Sun — at each Node. 

181. In 223 mean lunations, the Sun, Moon, 
and Nodes return so nearly to the same relative 
positions, that the Node will be within 0°28'12" of 
its original place ; at that interval, therefore, there 
will be a regular return of the same order of 
eclipses for many ages. The cycle is (Sec. 172) 



29.53059 x 223 ; equal to 18 years, 11 days, 7 hours, 
43 minutes, 3.64S seconds when Leap Tear is only 
four times included, and IS years, 10 days, 7 hours, 
43 minutes, 3.64S seconds when Leap Tear is in- 
cluded five times. In this period there are usually 
about seventy eclipses — twenty-nine of the Moon, 
and forty-one of the Sun ; but although the num- 
ber of Solar eclipses in this time is nearly as three 
to two of the Lunar, yet the Lunar eclipses visible 
at any one place are the most numerous, because 
the Lunar eclipse is visible to an entire hemisphere, 
while a Solar eclipse is only visible to a portion, 
and sometimes a very small part, of the Earth's 
enlightened side. 

185. Cheoxologt. — Our ideas of time are 
dependent upon the apparent motions of the lumi- 
naries, and our methods of measuring it are solely 
referable to them. The year is measured by the 
Earth's annual motion round the Sun. This is 
completed in Oh. 11m. 12.43s. less than 365^ days; 
we thus have three common years of 365 days 
each, and one Leap Tear, containing 366 days. 
But these four years measure 44m. 49. 72s. more 
than the time of four revolutions, which excess 
amounts to 18h.40m. in a hundred years, and this 
excess is allowed for by omitting three leap years 
in every four centuries. Therefore : 

To find the distance of any given year from 
Leap Tear, we divide the number of years since 
the Christian Era by 4 ; if nothing remains, it is 
Leap Tear ; if 1, 2, or 3 remains from the division, 
it is so many years after Leap Tear. But we 
count the even hundreds as common years, unless 
the number of centuries is exactly divisible by 4. 
Thus 1S75, divided by 4, leaves 3 as the number 
of years after Leap Tear; so 1700, 1800, and 1900 
are common years, but 2000 will be counted as 
Leap Tear, because 20 leaves no remainder after 
the division. 

The commencement of the year is fixed as being 



TIME, AND ITS MEASURES. 



11 



the time when the Earth is in Perihelion (Sec. 177), 
or as near thereto as is permitted by the even divi- 
sion of days into months. The subdivision of the 
year into 'mouths evidently corresponds to the 
nearest number of Lunations (Sec. 172) contained 
therein. They originally consisted of six months 
of 30 days each, and six of 31 days each ; but 
when Augustus, the Roman Emperor, named the, 
then, sixth month, after himself, he made it a long 
month, and took the added day from February — 
then a short month, and the last ; the year com- 
mencing with March. When it was subsequently 
found that the year was too long, the irregular 
month was chosen as the one to be further short- 
ened ; we now count 28 days in February, "Ex- 
cept in Leap Year, at which time, February days 
hath twenty-nine." In like manner, the Ecliptic is 
divided into twelve equal parts, or Signs, each 
being nearly the measure of the Sun's progress 
during one Lunation. 

The Day is, of course, a natural division of time, 
being the period of the Earth's rotation : its length 
is uniform, as measured by any two successive 
returns of a fixed star to the same meridian, but 
variable as measured by the Sun (Sec. 16) ; it may 
be regarded as a year in miniature. 

The subdivisions of a day are arbitrary, but their 
value is invariable ; the number of hours from 
noon to midnight was probably suggested by the 
number of months in a year. 

The Week — a collection of seven days — an- 
swers to the number of Planets and Luminaries 
known to the ancients ; and, from the very earliest 
period of the world's history, the days of the week 
have each been designated by the name of one of 
tho^e bodies. The week is also the nearest even 
number of days to the measure of the interval 
between two successive quarters of the Moon. 

18f>. Fifty-two weeks of seven days make 364 
days ; hence, the same day of the month will fall 



one day later in the week each year, unless the 
29th day of February intervenes, when it will fall 
two days later. Hence the following rule for find- 
ing the day of the week at any given date : 
Accounting the first day of January, in any year, 

as A, the 2nd as B , the 7th as G, and the 8th 

as A again, the letter upon which Sunday will fall 
is called the Dominical, or Sunday letter for that 
year. It is thus found : 

From 1700 to 1800 take the year, from 1800 to 
1900 take the year minus one, because 1800 was 
accounted a common year ; for the same reason, 
from 1900 to 2000 take the year minus two; from 
2000 to 2100 take the year minus two, because no 
additional day has been lost from the calendar. 
To the year, thus corrected, add its one-fourth 
part, omitting fractions ; divide the sum by 7 ; the 
remainder, subtracted from 7, gives the number 
answering to the Dominical Letter, or the day in 
the first week in January on which Sunday falls. 

Thus for 1875 we have *^L2=x + 1875 — 1 = 2342, 
which, divided by 7, leaves 4 remainder ; this 
taken from 7 leaves 3, answering to C as the Sun- 
day letter; or, Sunday falls on January 3rd, 1875, 
and, of course, on the 10th, 17th, 24th, and 31st of 
the month also. For «the 1st of each month the 
letters are as follows : January and October, A ; 
May, B ; August, C ; February, March, and No- 
vember, D ; June, E ; September and December, 
F ; April and July, G. Hence in 1875 the Sunday 
letter falls on the 1st of August, the 2nd of May, the 
3rd of January and October, etc. ; it must, how- 
ever, be noted that in Leap Years the Dominical 
Letter, thus found, answers only for the first two 
months ; for the rest, take the preceding letter. 
Thus, for 1872, the letters are G. and F. 

187. A Solar Cycle is found by multiplying 
together 4 — the number of years from Leap to 
Leap — and 7 — the number of years in which the 
Dominical letter would run through the week, if 



*8 



ASTRONOMY. 



there were no Leap Year. At the end of this 
period of 28 years, the days of the week fall on the 
same days of the month throughout the year ; 
hence, if Sunday fall on the 2nd of January in 
1870, it was the same in 1842, and will be so in 
1898. The Solar Cycle began 9 years before the 
Christian Era ; hence, to find the number of this 
Cycle, add 9 to the given year, and divide the sum 
by 28 ; the remainder is the number ; thus for 1875 
plus 9, the remainder is 8. 

188. Nineteen Solar years contain 6939.603016 
days, and 235 lunations are performed in 6939.- 
6881565 days; that is, in 19 years the Sun and 
Moon return to the same relative positions on the 
same day of the month, and within one hour and 
a half of the same instant. This is called the 
Metonic Cycle, or Golden Number. It com- 
menced one year before the Christian Era, there- 
fore, if we add one to the given year, and divide 
the sum by 19, the remainder is the Golden num- 
ber. But when a hundred year, not Leap Year, 
falls in this Cycle, the New and Full Moon will 
occur a day later than otherwise. The Golden 
Number for 1875 is 14. 

By combining the Solar and Lunar Cycles, we 
obtain the Dionysian Period of 532 years, at the 
end of which time the New and Full Moon return 
to the same days of the week and month. 

The Roman Indiction is a Cycle of 15 years, 
which began 3 years before the Christian Era. 
This is not an Astronomical Cycle, but is here 



mentioned as a component of the Julian Period, 
which is formed by the continual multiplication of 
these three Cycles — 28 x 19 x 15 = 7,980 years. 
The year 1800 was the 6,513th Julian Year: A. D. 
1875 is Julian Year 6,588. 

180. The Epact of any year is the Moon's Age, 
or the Number of days elapsed at the beginning of 
the year since the last New Moon. It is thus 
found : Multiply the Golden Number into 11, divide 
the product by 30 ; from the remainder (plus 30, 
if required) take 11 ; the remainder is the Epact. 
When the Solar and Lunar Cycles begin together, 
the Moon's age on the 1st of each month is as fol- 
lows : January, ; February, 2 ; March, 1 ; April, 
2 ; May, 3 ; June, 4 ; July, 5 ; August, 6 ; Sep- 
tember, 8 ; October, 8 ; November, 9 ; December, 
10 ; consequently, if to the Epact we add the 
number above, and the day of the month, their 
sum, if under 30, is the Moon's Age ; if above 30, 
the excess over 30 in months of 31 days, or the 
excess over 29, in months of 30 days, is the Moon's 
Age, or the number of days elapsed since the last 
preceding New Moon. Easter Sunday is the 
Sunday after the first Full Moon which occurs after 
the Vernal Equinox. Hence, 

To find the date of Easter, in any year, we must 
remember that the Equinox falls on March 21st in 
common years, and on March 20th in Leap Year. 
Find the nearest New Moon to this date, and 
reckon forward 15 days to the Full. The Sunday 
next succedin^ this is Easter. 



Define and explain (the figures refer to the sections) ; 

172. The Moou ; Sidereal period ; mean daily motion ; variable movement ; Synodic Revolution. 173. The Lunation ; 
Moon's Orbit ; New and Pull. 174. Moon's Latitude ; Retrogradatiou of Nodes. 175. Rotation on Axis ; Libration. 
176. Eclipses; when; limits. 177. Parallax; angle at the center; Angular Semidianicters of Earth and Sun; The 
Moon; Apogee and Perigee; Perihelion and Aphelion. 178. How to measure the Moon. 179. Lunar Eclipses ; Earth's 
shadow ; limit of distance from the Node ; Umbra ; Penumbra. 180. Solar Eclipses ; limits ; 181. Annular Eclipse ; 
place and motion of shadow. 182. Penumbral limit. 183. Number of Eclipses in the year ; the reason. 184. Lunar 
Cycle. 185. Chronology ; Leap Tear ; Day, Week, and Month. 186. Place of Sunday ; Dominical Letter. 187. 
Solar Cycle. 188. Metonic Cycle ; Golden Number ; Roman Indiction ; Julian Period. 189. Epact ; the Moon's Age ; 
Easter. 



ACTUAL DISTANCES AND VOLUMES. 



190, The distances and dimensions hitherto 
dealt with, are angular only (Sec. 22). Two stars 
may be seen at the same angular distance, whether 
a few thousand or many millions of miles apart. 
We shall now indicate the character of the pro- 
cesses by means of which we are enabled, approxi- 
mately, to measure the actual distances, sizes, and 
bulks, and comparative weights, of those bodies 
which are nearest to the Earth, and to fix certain 
limits of minima for those quantities in the case of 
the more distant. We pre-suppose a general 
acquaintance with plane and spherical Geometry, 
and plane Trigonometry. 

191, The Earth. — The rotation of the Earth 
on her axis is uniform with regard to the Fixed 
Stars, and nearly so in relation to the Sun (Sec.16). 
She presents every part of her Equatorial surface 
to the Sun once in about 24 hours. If we set a 
clock to the hour and minute of 12, at the exact 
instant of Noon at any place on the Equator, and 
then carry the clock Eastward till we arrive at 
some place where the same time movement shows 
one o'clock at the instant of Noon at the second 
place, it is evident that the two stations are one 
hour asunder, or one part in 24 of the Earth's cir- 
cumference on the Equator. The distance be- 
tween the two places being measured on the sea 
level, and multiplied into 24, the product is the 
perimeter of the Equatorial circle. 

This operation, or a similar one, has actually 
been performed, and the circumference found to 
be 24,899 English miles; the diameter (7925.6 
miles) is easily deduced from this by simple pro- 



portion; the half of the diameter, or radius is, 
more exactly, 20,923,599.98 English feet. 

Similarly : If we proceed along a circle of the 
meridian (Sec. 7) from the Equator towards either 
pole, and, by means of the different altitudes of 
the Sun, or some fixed star, find the angle formed 
on that circle by lines pointing to the Zenith of 
each place, we shall arrive at nearly the same re- 
sult ; but upon taking accurate observations in 
several parts of the meridian circle, we shall find 
a slight inequality in the lengths of equal arcs in 
this direction ; these quantities correspond to the 
different portions of the perimeter of an Ellipse, 
the longest axis of which lies in the plane of the 
Equator. The true figure of the Earth is hence 
that of an oblate spheroid, having its Polar diame- 
ter equal to 7899.1 miles. The Polar radius is 
20,853,657.16 English feet. 

192. This spheroidal shape is believed to be a 
consequence of the Earth's rotation on her axis. 
If the particles of matter of which she is com- 
posed were at some previous time in a fluid, or 
semi-fluid state, so as to allow a freedom of 
motion among them, the central tendency of the 
particles about the Equator would be partially 
counteracted by the whirling motion, or centrifu- 
gal force, generated there by the rotary movement, 
while the attractive force at the Poles, being un- 
diminished, would press in, and partially heap up 
the more Equatorial portions ; the comparatively 
small irregularities of the surface are traceable to 
other causes operating subsequently. Every star 
and planet sufficiently near, and large enough to 



80 



ASTEONOM Y. 



be measured, is found to be similarly affected — 
the Equatorial diameter being the greatest. 

193. A knowledge of the actual weight of the 
Earth is of little importance, and is probably un- 
attainable. Nevertheless, an attempt has been 
made to solve the problem. A precipitous cliff 
■was selected by Dr. Maskelyne, the internal com- 
position of which was known, and its weight ascer- 
tained by multiplying its cubic contents in feet, 
into the weight of one foot of its material ; the 
force of its attraction, as compared with that of 
the Earth's whole mass, was then tested by sus- 
pending a plumb line from its summit, and measur- 
ing the deflection from the perpendicular. 

From these observations the weight of the Earth, 
as compared with that of an equal bulk of water, 
has been estimated as 54 to 10. It is very proba- 
ble that the comparative weight, or specific gravity 
of the Earth, is not less than 5.4, nor greater than 
6. It is thus possible to compute her weight in 
tons, true to within about ten per cent, of the gross 
amount. 

191. The Moon. — If two stations on the 
Earth's surface, several degrees apart, be selected, 
and the position of the Moon among the Fixed 
Stars be observed from each at the same iustant, 
there will be found an appreciable difference. If 
the stations be so chosen that while the Moon is in 
the Zenith of one, she will be on the Horizon of 
the other, so that the line, A B, joining the cen- 
ters of the Earth and Moon will form the longer 
leg of a right angled plane triangle, whose shorter 
leg is, A D, the Earth's Radius ; then the angle 
A B D, at the Moon, will average about 0° 57' 20", 
and the angular Semidiameter of the Moon, the 
angle, B A C, will average 0° 15' 37.46", the pro- 
portion being as 3.6697 to 1 (Sec. 177) : Hence by 
the theorem that " the sines of the angles are jiro- 
portional to the opposite sides," we have 

Sine of ABD: AD : : Cosine of A B D : A B. 



Or Cotangent of B equals A B. Hence : Log Co- 
tangent of 0°57'20"' + Log of 3962. S = Log of 
237,626 miles ; or, calling 
A D equal to 1, the result 
is 59.96435 Semidiame- 
ters of the Earth. In 
the same way we may 
find the Moon's distance 
from the Earth at Peri- 
gee and Apogee, by tak- 
ing the greatest or least 
Parallax for the value 
of the angle at B (Sec. 
177). 

195. In the triangle 
ABC, we have known 
the side A B by the last 
proportion, and the angle 
at A equal to the Moon's 
angular semidiameter ; 
whence the lineal dia- 
meter of the Moon is 
found to be 2153 miles. 
The solid contents of 
globes being proportional 
to the cubes of their respective diameters, the vol- 
ume of the Moon is very nearly to that of the 
Earth, as the cube of 2153 to the cube of 7925.6; 
it is not exactly equal to the result thus found, 
because neither the Earth nor the Moon are perfect 
spheres, and the amount of departure from the 
true globular form is not precisely the same in each 
case. 

190. It has been ascertained, by repeated ob- 
servation, that at the time of the Moon's First 
Quarter, the Earth is about 0°0'6" in advance of 
the place in her orbit which she would occupy if 
the Moon were at the New or Full, and is the same 
angular distance behind Iter average place, if the 
Moon be in her last Quarter. That is : When the 




DISTANCE, DIMENSION, AND WEIGHT. 



81 



Earth is preceded in her orbit by the Moon, she is 
retarded, and when the Moon is behind in the 
order of the Signs, the Earth is pushed forward by 
this amount. Astronomers have concluded from 
this fact that it is not the Earth's center, but a 
point between it and the Moon, which describes an 
equable circuit around the Sun. 

In a subsequent section the distance of the Earth 
from the Sun, is stated as being a iittle over 91 
millions of miles, whence this angular disturbance, 
which averages a little more than 0°0'6", is found 
to correspond to about 2700 miles along the cir- 
cumference of the Earth's orbit. The Earth's 
Equatorial Semidiameter of 3962.8 miles has an 
angular value (Sec. 177) of 8".95 in the orbit, 
whence, by proportion, the angular value of 2700 
miles is a little more than 6". This distance from 
the center varies a little with the distance of the 
Moon from the Earth, but it is always in the posi- 
tion E, as in the diagram (Page 80). Around 
this common center of gravity the two bodies 
revolve each month, the point moving forward 
steadily in the Ecliptic. 

The motion of the Earth is hence something 
like that of an eccentric wheel, while that of the 
Moon is similar to what it would be, with a shorter 
radius of revolution, if the Earth advanced equa- 
bly. 

As the Earth and Moon thus balance each other 
on this common center of gravity, it follows, from 
the laws of mechanics, that their forces are equal ; 
that is : If the weight of each body be multiplied 
into its distance from the common center, the 
products will be equal. Dividing the Moon's dis- 
tance by that of the Earth, we obtain about 87f 
for the number of times that the Earth is heavier 
than the Moon, whence the Moon's weight is 
0.011399 when the Earth is taken as Unity. 

If an average cubic mile of the Moon were of 
the same weight as an average cubic mile of the 



Earth, a comparison of their volumes would show 
the Moon's relative weight to be much greater 
than the amount here given. Comparing the rela- 
tive weights with the relative bulks (Sec. 195), we 
find that the weight of the Moon is but 0.5657, 
where an equal bulk cut from the Earth would 
weigh 1. The last named fraction, therefore, rep- 
resents the Moon's comparative density ; and ac- 
cepting 5.4 (Sec. 193) as the specific gravity of the 
Earth, the Moon is about 3 times as heavy as an 
equal bulk of water. 

197. The SuxV. The Solar Parallax (Sec. 177), 
or the angle subtended at the Sun's center by two 
lines drawn to include the Semidiameter of the 
Earth, is 0° 0' 8".95 ; knowing the value of this 
angle, the distance of the Earth from the Sun can 
be calculated (Sec. 194) by multiplying the Cotan- 
gent of the parallax into the Earth's Semidiameter. 
But this angle is so small that it is very difficult to 
measure it, and an error of one-tenth part of a 
second in the observation would involve an error 
of a million of miles in the distance. Other means 
have, therefore, to be resorted to than those used 
in the case of the Moon. 

Astronomers have had recourse to the motions 
of the planet Venus, for a determination of this 
angle from one much greater. The mean angular 
distance of Venus, at her greatest elongation from 
the Sim is 46° 20', which (Diagram, Page 66) is 
manifestly the time when she is in such a position 
in her orbit as to be at the right angle of a tri- 
angle, the hypothenuse of which is the Earth's 
distance from the Sun. Hence, by trigonometry, 
the sine of the angle of elongation, is her mean 
distance from the Sun, that of the Earth being 
taken as Unity. The natural Sine of 46° 20' is 
0.7233317 nearly, which is the proportional dis- 
tance of Venus from the Sun ; the complement of 
this, or 0.2766683, is her proportional distance 
from the Earth at the time of Inferior Conjunction. 



A S TEON MY. 



If, now, at the time of a transit of Venus over 
the Sun's disc (Sec. 163), observations be simul- 
taneously taken at two different stations on the 
Earth's surface, the edge, C, of the planet will 
appear to the observer at A, as on the Sun's disc 
at D, and 
will appear 
at F as seen 
from B. 
The exact 
angular 
measure of 
the whole 
disc, N M, 




known, and 
that portion 
which lies 
between D 
and F is 
found by 
substract- 
ing there- 
from the 
sum of the 
ob served 

distances, X F and D M ; the remainder, F D, 
when increased in proportion as C is nearer than 
A is to S, is the measure of the angle at C. The 
right line joining A and B is measurable, its ex- 
tremities lying in the Earth's surface. 

If at the time of transit, the line A B be equal 
to the Earth's radius, or 3962.8 miles, and the ob- 
served angular distance, D F, equal to 23". 4 ; this 
divided by C D, or 0,7233317, will give the angle 
at C equal to 32^"; the cotangent of half the 
last angle multiplied into half the base, will give 
the distance of the Earth from Venus as about 
25,268,000 miles ; whence, by proportion, the dis- 
tance of Venus from the Sun is 66.060,000, and 



1 the Sum of the two gives 91,328,000 miles as the 
| Earth's mean distance, from which, as Cotangent 
to the Earth's Radius, the Solar Parallax is given 
as 8".95. 

Observations similar to these were made at the 
times of transits of Venus in the years 1761 and 
176'.); the processes employed were similar to 
those here indicated, though not identical with 
them. The results arrived at were not precisely 
the same as now stated, but they have been cor- 
rected by subsequent observations of other bodies. 
Venus transits the Sun's disc twice during the 
present century —December 9th, 1874, and De- 
cember 6th, 1SS2 ; the phenomena will be observed 
more accurately than in the last century, and it is 
believed that the results will not be materially dif- 
ferent from those above given. 

198. We can now calculate the diameter of the 
Sun, as we have already found that of the Moon 
(Sec. 194). His apparent semidiameter averages 
0°16'1".S2, the tangent of which angle is the lineal 
semidiameter of the Sun to the mean distance as 
radius. Thu 



Angular semidiameter=0=16TS2 ; Tangent is 7.C68672 
Mean distance (Sec. 197) 91,328,000 ; Log add 7.960604 

Semidianieter=42o,S68 miles ; Log is 5.629276* 

Twice this amount is 851,736 miles, the Sun's 
actual diameter. 

The process of weighing the Sun is a much 
more delicate operation than in the case of the 
Moon, as a greater number of elements enter into 
the calculation. The principle is, however, the 
same, the Sun being weighed against the planetary 
bodies and the Earth, by noting the amount of 
their displacement in certain relative positions. 
His weight is found to be 354,936 times that of 
the Earth ; and on comparing the two masses, we 
find that his density is but 0.284-that of the Earth 
being unity; or it is 1.533 as compared with an 
equal bulk of water as unity. 



DISTANCE FROM THE SUN. 



83 



The distance of Venus, at the time of transit, 
being known (Sec. 197) we can calculate her diam- 
eter and bulk, as in the case of the Sun. These, 
values, for all the principal members of the Solar 
family, are given in a subsequent table. 

199. The mean angular semidiameter of the 
Sun has been used in this calculation, but this 
angular magnitude varies (Sec. 177) from 0°16'18".2 
about the 2nd of January, to 0°]5'46" about the 
2nd of July. We conclude from this that the 
Earth is in Perihelion at the first mentioned time, 
and in Aphelion six months afterwards, as there 
can be no doubt that the actual magnitude of the 
Sun is the same at all times, and that the differ- 
ences in apparent diameter are caused by our 
relative nearness or departure further from him. 
(See diagram on this page.) We conclude that the 
orbit of the Earth is not an exact circle, and that 
the Sun is not in its exact center. 

The length of the Radius Vector — the distance 
from the Sun — at any point, being the cotangent 
of the angle of apparent semidiameter (Sec. 194), 
the Earth's radius being assumed as unity ; the 
proportion between the cotangents of the greatest, 
mean, and least values, of the angle, gives the rela- 
tive distances, or corresponding Radii Vectores, as 
1.016751 for the Aphelion, and 0.983249 for the 
Perihelion, where the mean distance is 1. The 
difference is not large enough to be appreciable on 
a small scale. The following diagram shows, in 
exaggerated form, the difference in the angle 
under which the Sun's semidiameter is seen as 
viewed from E, the Aphelion, and C, the Peri- 
helion : 

200. Equal Areas in Equal Times. — The 
mean daily motion of the Earth in her orbit (Sec. 
12) is 0°59'8".33 ; but this motion is not uniform, 
being most rapid at the Perihelion, and slowest at 
the Aphelion. We find by observation that this is 
the case with all the heavenly bodies, and that the 



rate of motion in the orbit bears a well defined pro- 
portion to the distance from the body around which 
the revolution is performed. 

If the circumference of tha orbit be divided into 
lengths, as E F, H K, D C, in the accompanying 
diagram, each of which is passed over in the same 
space of time, the product of the mean Radius 
Vector of each division into the lineal length of its 
corresponding arc, is a constant quantity. That 
is: SLxEF=SNxHK=S MxC D; and be- 
cause the area of a triangle with either a straight 




line or arc of a circle for its base, is half the pro- 
duct of the base into the height, therefore the 
areas of all the equal-timed triangles drawn in the 
orbit, as above, are equal to each other, and the 
planet, or Moon, describes equal areas in equal 
times. 

201. If equal areas are described in equal 
times, then unequal areas are proportioned to the 
times of describing the arcs at the circumference, 



84 



ASTKONOM Y. 



which form the bases of the triangles ; and because 
similar plane figure? have their areas proportional 
to the squares of their like dimensions, therefore 
similar triangles are proportional to the squares of 
the Radii Vectores. 

In the two similar triangles S R Z, S P V, hav- 
ing equal arcs in different parts of the orbit, the 
times are proportional to the areas, and therefore 
to the squares of the Radii Vectores. 

The force with which a body moves, being 
directly proportional to its velocity, is inversely 
proportional to the time, which increases as the 
velocity decreases. The relative force of motion 
at any point in the orbit is, therefore, inversely pro- 
portional to the square of the Radius Vector. 

202. The Law of Attraction. — The univer- 
sally accepted theory of the motion in the orbit is 
that it is the result of two forces, both acting in 
straight lines, at right angles to each other. A 
body once set in motion in the direction P to T, 
would move forward through the point W, and 
beyond it, in an unvarying straight line, if there 
were no other force operating ; but we know that 
all masses of matter attract each other, as the 
Earth attracts a projected stone, and finally arrests 
its motion, only because the velocity of the stone 
is retarded in its passage by the atmosphere, and 
is at last overcome by the Earth's attraction. 

A planet at P tends to move to T, but during 
the time due to describing the line P T, the attrac- 
tion of the Sim has exercised a force equivalent 
to drawing the planet from T to V, and, in obe- 
dience to the two forces, the planet passes along 
the curve P V ; the same forces constantly opera- 
ting, the curve, P V, is many times reproduced till 
the planet has passed entirely round the Sun and 
is again at P. This second power we call the 
Attraction- of Gravitation - . 

In order that a re-entrant curve shall be the re- 
sult of the two forces, the attraction must always 



correspond in its variation of intensity to the force 
of motion in the orbit; that is: The force by 
which the body moves from P to V. must vary 
exactly as the attraction which draws the planet 
from T to V ; if it were otherwise, the attraction, 
being at any time the strongest, would contiuue 
so, and finally draw the planet to the center, while 
if the attraction were weakest the balance could 
not be recovered, and the planet would continually 
enlarge its orbit, till ultimately it woidd cease to 
revolve, and move off in a straight line. But the 
force of the motion in the orbit is (Sec. 201) in- 
versely proportional to the square of the Radius 
Vector at any point, and the attraction must, there- 
fore, at every point, be also inversely proportional 
to the square of the Radius Vector. In other 
words, the force of attraction increases as the 
square of the distance decreases. 

The application of this law is universal. If we 
compute the Moon's orbit we find that her deflec- 
tion from a right line — a tangent to the orbit — 
averages 0.053 of an iuch per second of time, 
while a stoue let fall near the Earth's surface will 
descend through a space of 193 inches in the same 
time. The distance of the Moon from the Earth's 
center (Sec. 194) is 59.96435 radii, or nearly 60 
times as far distant as the Stone, and the distance 
— as TV — through which the Moon falls, is to 
the Stone's fall as the square of 1 to the square of 
60, nearly. 

203. Ratio of Distance.— If we compare 
the relative fall of two or more planets towards 
the Sun, we find the same law operating. The 
diagram on Page 82 represents portions of the 
orbits of the Earth and Venus. While the Earth 
is passing from A B to K, Venus describes the arc 
from C to W ; the fall of the Earth from E to K 
bears the same proportion to V W, the fall of 
Venus in the same time, as the square of S W 
bears to S K; that is: The force of attraction to 



LAWS OF PLANETAKY MOTION. 



85 



the Sun is inversely proportional to the square of 
the distance from him. The proportion is easily 
verified by remembering that lines from S, to V and 
to E, are the Secants of the angles at the center, 
and that the Secant, diminished by Radius, gives 
the line of fall, which measures the force of the 
attraction. 

Similarly: If we watch the planet Jupiter 
(Sec. 157) we find that the differences in his an- 
gular Semidiameter (Sec. 199) indicate that when 
in conjunction he is one-half more distant from the 
Earth than when in Opposition. That is : If when 
in Opposition the distance of Jupiter from the 
Earth be represented by 4, the distance is increased 
to 6 when in conjunction ; but this difference is 
manifestly equal to twice the radius of the Earth's 
orbit, or Jupiter is 5.2 times farther from the Sun 
than is the Earth. The square of 5.2 is about 27, 
and, therefore, if the law hold good, Jupiter fal'^s 
one foot towards the Sun, while the Earth falls 
27 feet. Calculating his orbit on this basis, we 
find that it would carry him round the Sun in a 
little less than 12 years, and this result is confirmed 
by observation (Sec. 157). 

If, now, we compare the times of Sidereal Revo- 
lution of the Earth, Venus, and Jupiter, with the 
relative distances as already found, we shall dis- 
cover that they are related by a rather intricate 
proportion ; the cube of the mean distance of each 
in miles, divided by the square of the number of 
days of Revolution, is equal in each case, and the 
same j)roportion is found to exist between every 
member of the system. The law is usually thus 
expressed : The squares of the Times are propor- 
tional to the cubes of the Distances. 

204. By means of the preceding analogy, we 
can compute the actual distance from the Sun, of 
every member of the Solar system, having found 
its time of Sidereal Revolution by observation, and 
knowing the distance of the Earth or Venus (Sec. 



197). From the apparent magnitude we can then 
calculate the actual diameter of each, while its 
comparative weight and density are ascertained 
by the more complicated process referred to in the 
case of the Sun (Sec. 198). The amount of dis- 
placement of any one member of the great family 
from its average path, can only be ascertained by 
an observation of all. The Sun, for instance, tends 
to oscillate around a point between it and the 
Earth (Sec. 196), but he also tends to oscillate 
around a point between himself and Jupiter, and 
the same with all the other planetary bodies. So 
when Venus is in line between the Earth and Sun, 
her attraction acts with that of the Sun, and 
draws the Earth some distance within its mean 
orbit, while the attraction of the Earth, acting 
against that of the Sun, but not so powerfully, 
draws Venus some distance outside of her average 
orbit; when Venus is in advance of the Earth, as 
at E E (Page 66), the mutual attraction retards 
the motion of Venus in her orbit, and accelerates 
that of the Earth, and the contrary effect is pro- 
duced when the Earth is in advance, as at A A. 

Every member of the system is thus eternally 
swaying back and forth, deviating first in one 
direction and then in another, in obedience to the 
ceaseless play of mutual attraction, but prevented 
from losing its own orbit by the original forward 
impulse. Several of these perturbations are some- 
times acting in nearly the same direction, while at 
other times they counterbalance each other so 
accurately that no one is swayed out of the place 
it would occupy were there no disturbing influence. 

205. Nutation and Pbecession. — We are 
now prepared to comprehend, in part at least, the 
causes of the apparent irregularities in the Lunar 
motion (Sec. 172, and following). Reference to the 
diagram (Page 72) will show that the Moon moves 
absolutely over a greater space in her second 
and third quarters than the average motion, be- 



86 



ASTRONOMY. 



cause she is then progressing faster than the Earth, 
while in the other two quarters it is less than the 
mean, as she is then falling behind the Earth 
though still going forward, because, in the two 
weeks from third to first quarter, the earth passes 
over a much greater space in her own orbit than is 
measured by the diameter of the Moon's orbit. 

At the Full Moon the Sun and the Earth are 
both acting upon her in the same direction, short- 
ening her Radius Vector, and still further accele- 
rating her speed ; at the New Moon the attraction 
of the Sun lengthens her Radius Vector, pulling 
her away from the Earth ; and when in the third 
quarter the Sun hastens her motion, and retards it 
when she is in the first quarter, as he is then pull- 
ing her back partially in her course. If the Moon 
have latitude at the New or the Full, that is affect- 
ed also by the Solar attraction. 

In the next diagram the Sun is supposed to 
lie beyond S, the converging lines all meeting at 
his center; M represents the Earth's center, D the 
Moon at Full; I M D her latitude. The Solar 
attraction operates in the direction D to S, draw- 
ing the Moon to E, and increasing her apparent 
latitude to I M E. At the New Moon, C, the lati- 
tude is diminished to S M N, and a corresponding 
variation is necessarily produced in every other 
part of her orbit. 

The Solar attraction thus causes variations in 
both the longitude, latitude, and distance of the 
Moon, aiding, or counteracting partially, the at- 
traction of the Earth; and because the relative 
attraction is measured by the weight of the attract- 
ing body divided by the square of its distance 
(Sec. 202), a knowledge of the comparative weights 
and distances of the three is required to calculate 
the difference between the average — or mean — 
and the true place of the Moon at any time. 

200. If the Earth were stationary, the places 
of the Lunar Perigee and Nodes (Sec. 174) would 



be always the same, coinciding with the place of 
the Full Moon ; but in consequence of the Earth's 
Annual Motion, the Moon's Sidereal and Synodical 
Periods (Sec. 172) are not the same. Hence, the 
points of greatest attraction are continually 
changing — circulating round her orbit — and pro- 
ducing a revolution of the places of Perigee and 
Nodes, backwards through the signs. 

207. The play of these mutual attractions (Sec. 
204) affects not only the position of the Earth as 
a mass, but the position of the axis itself, or its 
inclination to the plane of the Ecliptic (Sec. 22). 

Let V M R represent the Earth's ^ D 

greatest or Equatorial diameter. 
Then, of the protuberant mass 
about the Equator (Sec. 192) the 
portion at R will be more strongly 
attracted than the part at V, by 
the Sun beyond S, and the ten- 
dency of the attraction is to 
cause the two planes to coincide, 
bringing R V into the direction 
IS. 

This force, however, is not con- 
stant, for V R represents the 
position only in midsummer and 
midwinter; at the Equinoxes the 
axis is perpendicular to I S, and 
the attractions are equal. Hence, 
the inequality increases from the 
Equinox to the Solstice, and 
thence diminishes gradually back 
to the time of the Equinox. The 
effect of this is a slight annual 
diminution in the angle between 
the Ecliptic and Equator, and 
also a vibration, or nodding, of SUN 

the Earth's axis — hence called Nutation. 

The Lunar attraction also operates, sometimes 
in the same direction with the Sun, as when at C 



PERTURBATIONS THE TIDES. 



or D ; at other times partially counteracting his 
influence ; and as the places of her Nodes change 
through the Signs, the situation of the greatest 
disturbing force varies also. Following the Lunar 
disturbing power, the Earth's axis describes a 
small circle of about 18" in diameter, in the same 
period as the Lunar Nodes (Sec. 174), and in the 
same direction — backward in the order of the 
Signs. 

The swaying motion of the Moon (Sec. 196), also 
swings the Earth a little out of the plane of the 
Ecliptic when the Moon is in her greatest latitude, 
causing the Sun to appear to be not more than 4" 
on the other side of the Ecliptic, or average an- 
nual path of the Earth among the Fixed Stars as 
seen from the Sun. 

208. The periods of the Luminaries being in- 
commensurable — i.e. — no assignable number of 
revolutions of the one exactly measuring the 
period of the other, the result of their combined 
attraction on the Earth, is a gradual shifting of 
the points of intersection of the Ecliptic and Equa- 
torial planes, as in the case of the Lunar Nodes, 
and in the same direction, but so much more 
slowly that 25,750 years are occupied in one revo- 
lution. The rate of change is about 50^" annually. 
This movement is called The Precession of the 
Equinoxes (Sec. 25). 

The period of 365 days, 5 hours, 48 minutes, 49 
seconds, is the time of revolution from the Equinox 
round to the Equinox again — it is called a Tropical 
Year, as measuring the regular recurrence of the 
Seasons — but during this time the Equinox has 
receded 50^", which distance has yet to be passed 
by the Earth ere she arrives at the original point, 
as referred to the Fixed Stars ; this occupies about 
20 minutes of time, so that we have another revo- 
lutional period called the Sidereal Tear, of 365 d 
6h 9m, or more exactly, 365.2563744 Solar days 
(Sec. 157.) 



209. The Tides. — The attractions of the 
Luminaries not only cause changes in the position 
of the Earth as a mass, but produce changes on 
her surface. The waters of the ocean are heaped 
up directly under the Moon's apparent path in her 
diurnal journey, the point of greatest elevation 
following her from West to East, and shifting back 
and forth across the Equator, as the Moon's decli- 
nation varies, during each lunation. This is called 
the Tidal Wave. 

In the open ocean the crest of the wave moves 
from East to West, on the circle of Latitude which 
corresponds to the Moon's declination, but about 
46° degrees behind the line joining the centers of 
the Earth and Moon ; the time of high tide being 
therefore about three hours (Sec. 26) later than 
the time of the Lunar culmination (Sec. 137). 
Directly opposite, at the antipodes of this wave, 
another protuberance of waters is met with. 
From each of these summits, the waters slope down 
in all directions, till at a distance of 90° from each 
there is a corresponding depression of the waters 
below the natural level. 

210. These points of greatest pi'otuberance 
and depression move round the Earth once in 
about 24 hours 53 minutes, that being the average 
interval of time between two successive returns of 
the Moon to the meridian of any place (Sec. 172). 
Hence at any place on the ocean, the two points of 
elevation succeed each other at mean intervals of 
12h 26m, and the points of depression succeed at 
the same intervals, giving an average time of 6h 
13m between the occurrence of high and low tide. 

In the open ocean the direct high tide — the 
first mentioned — is 3 hours behind the Moon, 
but where its flow is obstructed by a continent, ox* 
retarded in the passage through narrow inlets, the 
interval between the meridian passage and the 
high tide is changed, so that each place on the 
sea coast has practically its own time of high tide. 



ASTRONOMY. 



211. The cause of the direct tide is found in 
the greater distance of the Moon from the Earth's 
center, than from the waters on the surface. The 
difference is equal to the Earth's radius (Sec. 191) 
— nearly 4,000 miles. The water is, therefore, 
attracted more strongly than the Earth (Sec. 203), 
and is partially heaped up, falling behind the per- 
pendicular line in just the same way that a weight 
suspended by a long string, will hang back when 
the upper end of the string is carried rapidly for- 
ward. The opposite protuberance is usually as- 
cribed to the greater attraction of the Moon for 
the Earth's center than for the waters of the 
ocean nearly 4000 miles further distant. 

That the elevation of the waters is due to the 
Lunar attraction, is proven by the fact that the 
elevation varies with the distance of the Moon 
from the Earth. The comparative heights of the 
wave are nearly as follows : Moon at mean distance, 
51 ; Moon in Perigee, 59 ; Moon in Apogee, 43. 

212. The height of the tides varies also with 
the position of the Moon with reference to the Sun. 
The attractive power of the Sun for the whole 
Earth, as a mass, is 210.8 times that of the Moon, 
but the differences in his attractive power are much 
less, owing to his greater distance ; that is, 91,328,- 
000 miles, compared with 91,328,000 minus 3963, 
shows a much less ratio than 237,626, compared 



with 237,626 minus 3963. The attraction of the 
Moon at her mean distance being represented by 
51 (Sec. 211), that of the Sun will be equal to 20 ; 
at the Earth's Perihelion distance, 21; at the 
Aphelion, 19. 

"When the Sun and Moon are both acting in the 
same direction — as at the time of New or Full 
Moon — the tide rises higher, the mean height be- 
ing then represented by 20 plus 51 (= 71), the 
sum of the numbers measuring the attractions of 
the Luminaries ; this is called Spring Tide. At the 
time of the First and Third Quarters, the Sun is 
operating to elevate the depressions caused by the 
Moon, and the mean height of the tide is represent- 
ed by the difference of the numbers: 51 minus- 
20 (= 31) ; this is called Neap Tide. If the 
Luminaries be both at their greatest distance from 
the Earth at the time of Neap Tide, the differ- 
ence becomes (43 — 19) 24; if both be at their 
least distance at time of Spring Tide, the sum is 
(21 + 59) 80. The greatest tide is to the least, as 
80 to 24; or as 10 to 3. 

Where the tidal wave reaches a narrow bay or 
inlet through a wide channel, the tide rises to a 
greater height, the water rushing in much more 
rapidly than it can flow away. The average height 
of the tide decreases as the latitude of the place 
increases its distance from the crest of the wave. 



Define and explain (the figures refer to the sections): 

190. Actual (listeners, bulks, and weights. 191. The Earth ; Equatorial and Polar Diameters. 192. Spheroidal shape ; 
inferences. 193. Earth's actual weight; as compared with water. 194. Mean distance of Moon from Earth. 195. 
Moon's diameter and volume. 196. Her weight and density 197. Distance from the Sun ; mode of finding Solar Par- 
allax ; transit of Venus ; her distance. 198. Size and weight of Sun. 199. Perigee and Apogee ; lengths of Radii Vec- 
tores. 200. Equal Areas in Equal times. 201. Proportion of time and force to square of Radius Vector. 202. The 
law of attraction ; the Moon's fall per second; fall of a stone ; their ratio. 203. The Earth, Venus, and Jupiter; com- 
parative velocities and attractions to the Sun ; the Squares of the Times proportional to the Cubes of the Distances. 204. 
Mutual attractions, and ceaseless perturbation ; weight of the Planets. 205. Nutation and Precession ; cause of irregu- 
larities in the Lunar Motion. 206. Revolution of Moon's Perigee and Nodes. 207. Nutation of the Earth's Axis; 
208. Precession of the Equinoxes, Tropical and Sidereal years. 209. The Tides; position of Wave Crest. 210. Points 
of high and low tide ; intervals. 211. Causes; ratio of force at Perigee and Apogee. 212. Sun's attraction; Spring 
and Neap Tides. 



ELEMENTS OF THE 80LAE SYSTEM. 89 

213. The following tables show the distances, magnitudes, and bulks, with other elements of the 
orbits, of the leading members in the great Solar family. The quantities are taken from the astro- 
nomical works of Watson, and Loomis, but are modified to correspond with the recently an- 
nounced change in the estimated value of the Solar Parallax, and adapted to the beginning of the 
year 1875. The first table gives the elements of magnitude of the planetary orbits. The mean, greatest 
(Aphelion), and least (Perihelion), distances from the Sun are represented in comparison with the 
Earth's mean distance as Unity. The eccentricity of each planet's orbit is given in decimal parts 
of half the longest diameter of its own Orbit. 



Distance from the Sun. 



Mercury, 
Venus, 
Earth, . 
Mars, . 
Jupiter, 
Saturn, 
Uranus, 
Neptune, 



0.387098 
0.723332 
1.000000 
1.523692 
5.202776 
9.538786 
19.182390 
30.070552 



0.466687 
0.728261 
1.016751 
1.665964 
5.453961 
10.072187 
20.077455 
30.326040 



0.307510 
0.718403 
0.983249 
1.381420 
4.951591 
9.005385 
18.287325 
29.815064 



0.205603 
0.006814 
0.016751 
0.093374 
0.048281 
0.055919 
0.046661 
0.008496 



35,353,000 
66,060.000 
91,328,000 
139,156,000 
475,158,000 
871,163,000 
1,751,893,000 
2,746,300,000 



The following table gives the elements of Motion ; the Sidereal Revolution, or the time in days, and 
decimal parts of a day, occupied in making the circuit from any star, round to the same star again ; the 
Synodical Revolution, or the interval between any two successive conjunctions with the Sun as seen 
from the Earth ; the average motion in the orbit during each earth-day, the length of the day of each 
body, and the ratio of difference between the Equatorial and Polar diameters. 



Name. 


Sidereal 
Revolution. 


Synodical 
Revolution. 


Mean 
Daily Motion. 


Rotation on Axis. 


Compression. 


Mercury, 

Venus, 

Earth, 

Mars, 

Jupiter, 

Saturn, 

Uranus, 

Neptune, 

Sun, 


87.969282 

224.700775 

365.256374 

686.979456 

4,332.584803 

10,759.219711 

30,686.820556 

60,126.722000 

days. 


115.877 
583.920 

779.936 
398.867 
378.090 
369.656 
367.488 
days. 


245' 32.6" 

96' 7.8" 
59' 8.3" 
31' 26.7" 
4' 59.3" 
2' 0.6" 
42.4" 
21.6" 


24h 5m 28s 
23h 21m 21s 
23h 56m 4s 
24h 37m 22s 

9h 55 m 26s 
lOh 29m 17s 

9h 30m? 
not known. 
607h 48m 


■fa 

TT 
TV 



The following table shows the relations of position in the orbit; the longitude of the planet when 
nearest to the Sun (the longitude of the Aphelion is in the same degree and minute of the Opposite sign) ; 



and the point where the planet 



the Ecliptic from South to North Latitude (the South Node 



90 



ASTRONOMY. 



is in the same degree and minute of the Opposite Sign) ; the third and fourth columns give the annual 
movement forwards ( + ) or backwards ( — ) along the Ecliptic, as referred to the Fixed Stars ; in addi- 
tion to these variations, the Longitudes of the Perihelion and Nodes are increased at the rate of 50J" 
each year by the Precession of the Equinoxes. The sixth column shows the angle made by the plane 
of the Orbit with the plane of the Ecliptic, the points of intersection being at the Nodes. 





Place of 


Annual 


Place of 


Annual 


Inclination 


Annual 


Name. 


Perihelion. 


Variation. 


North Node. 


Variation. 


of Orbit. 


Variation. 


Mercury, . . 


n 15° 30' 48" 


+ 5.84" 


« 16° 50' 39" 


— 7.82" 


7° 0' 18" 


+ 0.181" 


Venus, . . 


a 9° 42' 32" 


— 2.68" 


II 15° 33' 6" 


— 18.71" 


3° 23' 32" 


+ 0.045" 


Earth, . . . 


® 10° 46' 38" 
JXf 3° 45' 28" 


+ 11.81" 
+ 15.82" 




— 23.29" 


1° 51' 6" 




Mars, . . 


» 18° 33' 16" 


— 0.003" 


Jupiter, . . 


T 12° 18' 47" 


+ 6.65" 


® 9° 21' 27" 


— 15.81" 


1° 18' 35" 


— 0.226" 


Saturn, . . 


23 0° 35' 23" 


+ 19.37" 


® 22° 34' 37" 


— 19.42" 


2° 29' 24" 


— 0.155" 


Uranus, . . 


TIE 18° 36' 8" 


+ 2. 4" 


n 13° 17' 9" 


— 36. 0" 


0° 46' 30" 


+ 0.031" 


Neptune, . 


« 14° 19' 28" 




ail 9' 30" 




1° 47' 2" 





The following table shows the diameter in miles, and the angular diameter of each body, in seconds^ 
Avhen at the mean distance from the Earth ; the weights of each as compared with those of the Sun 
and Earth, and the Densities as compared with that of the Earth, and with equal bulks of water. 





Diameter in 


Weight 
Sun = 1. 


"Weight 
Earth = 1. 


Density 
Earth = 1. 


Density 




Miles. 


Seconds. 


Water = 1. 


Sun, 


851736 


1923.6" 


1.000000 


354936. 


0.284 


1.533 


Mercury, .... 


2960 


6.7" 


T-sriiTT 


0.0729 


1.3'J2 


7.518 


Venus, 


7566 


17.1" 


TsnrVtnj 


0.9101 


1.032 


5.572 


Earth, 


7925.6 




3 S Ja 3 6 


1.0000 


1.000 


5.4 


Mars, 


3900 


5.8" 




0.1324 


1.105 


5.965 


Jupiter, .... 


88316 


38.4" 




338.718 


0.258 


1.393 


Saturn, 


71936 


17.1" 




101.364 


0.149 


0.804 


Uranus, .... 


34704 


4.1" 




14.252 


0.19 


1.025 


Neptune, .... 


32243 


2.4" 


T5T80 


18.98 


0.335 


1.807 



The followii 



i the Elements of the Moon, and of her Orbit. 



Mean Distance in Radii of Earth, 59.96435 

Mean Distance in Miles, 237,626 

Eccentricity of Orbit, 0.054844 

Diameter in Miles, 2153 

Angular Semidiameter, 14' 44" to 16' 46" 

Weight (Earth = 1), 0.011399 

Weight of Earth and Moon (Sun being 1), — 



Sidereal Revolution, days, 
Synodical Revolution, 
Inclination of Orbit, 
Revolution of Nodes, days, 
Revolution of Perigee, 
Density (Earth = 1), 



5° 8" 47.9" 
6798,28 

3232.57534 
0.5657 
~5~5iTT5 



OTHER MEMBERS OF THE FAMILY. 



214:. Planetoids. — A great number of smaller 
bodies have been discovered within the present 
century, revolving around the Sun in orbits be- 
tween those of Mars and Jupiter. Four of these 
— named Ceres, Pallas, Juno, and Vesta — were 
known as early as 1S07 ; their periods of revolu- 
tion vary from 3 years 7\ months to 4 years 7\ 
months, and their average distances from the Sun 
are so nearly the same that their orbits may be 
compared to a number of hoops of nearly equal 
size, each intersecting every other in two oppo- 
site points. They received the name of Asteroids 
(star-like), and have since been called Planetoids 
(planet-like). 

For thirty-eight years these four were supposed 
to be the only members of this singular sub-family 
of bodies, but in 1845 a fifth was found, and since 



then the number has been increased to about 100 ; 
to the end of 1866, ninety-one had received names. 
The orbits of all these bodies have been compu- 
ted, but it is not necessary here to give directions 
for finding them among the fixed stars. The orbit 
of Vesta is relatively so small that she is some- 
times much nearer the earth than any other of the 
larger Planetpids, and is then faintly visible as a 
white star-like body of the 6th magnitude. The 
others are, at all times, invisible to the naked eye. 

The orbits of about one-third of the number 
form angles of more than 8 degrees with the plane 
of the Ecliptic, and consequently are often outside 
the Zodiacal limits. (Sec. 27). The inclination of 
the plane of Pallas' orbit is nearly 35 degrees. 

21o. The following are the elements of the 
principal Planetoids, for the end of the year, 1856 : 



Planetoid 


Ceres. 


Pallas. 


Juno. 


Vesta. 


Discovered. 


January 1, 1801. 


March 28, 1802. 


September 1, 1804. 


March 29, 1807. 


Mean Distance, 


2. 765765 


2.769533 


2 668611 


2.360559 


Eccentricity, .... 


0.079180 


0.239045 


0.256535 


0.090101 


Sidereal devolution; days, 


1,680.047 


1,683.481 


1,592.305 


1,324.710 


Perihelion, .... 


a 29° 34' 


SI 2° 4' 


« 24° 8' 


t 10° 46' 


North Node, .... 


LI 20° 48' 


TIB. 22° 38' 


TIB 21° 0' 


® 13° 24' 


Inclination of Orbit, 


10° 36' 


34° 43' 


13° 3' 


7° 8' 


Diameter in miles, 


283 


214 


140 


284 


Apparent Magnitude, 


8th 


7th 


8th 


6th 



Another sub-family of Planetoids is believed to 
revolve rapidly round the Sun within the orbit of 
Mercury, and still another band of much smaller 
bodies revolve in a very prolonged elliptic orbit, 
which, at the side nearest to the Sun, crosses the 



Earth's path at a point passed by her in August, 
and at the other side stretches far away beyond 
the orbit of Neptune (See Sec. 220). A second 
orbit, similar to the last named, is believed to be 
partially filled up, the Planetoidal particles per- 



ASTRONOMY. 



forming one revolution in about 33^ years, and 
forming a band of at least 50,000 miles in thick- 
ness, and 1,000,000,000 miles in length, or about 
one-fourth the circumference of the entire orbit. 
This crosses the Earth's path at a point passed 
over by her in November. It is highly probable 
that thousands of other zones, or parts of zones, 
revolve around the Sun at different distances, and 
it is more than possible that our Earth has a like 
accompaniment. The planet Saturn is surrounded 
by an immense ring of matter, so dense that it has 
been thought to be solid, but it has appeared at 
times to be divided into three or more bands, and 
is undoubtedly composed of separate bodies, all 
revolving around the planet in an annular orbit. 

216. Satellites. — Several of the Planetary 
bodies are themselves centers of revolution for one 
or more worlds. The Earth is attended by the 



Moon, and it is considered probable that she has 
another, but very small, attendant, revolving 
around her at about two-fifths the distance of the 
Moon. Neptune has one satellite, Uranus six or 
seven, Saturn has eight, besides a zone of Moon 
matter (Sec. 215), and Jupiter has four. These 
Satellites all revolve about their primary planet, or 
rather about their common center of gravity (Sec. 
196), and accompany it in its journey around the 
Sun. After our own Moon the Satellites of Jupi- 
ter are of the greatest interest to us, as the instant 
of their apparent contact with the edge of the 
planet is frequently watched by the navigator for 
the purpose of finding the difference in time, and 
hence the distance (Sec. 191), between two differ- 
ent points on the Earth's surface. 

217. The following are the elements of the 
four Moons of Jupiter : 



No. 


Sidereal Revolution. 


Distance in 
Radii of Jupiter. 


Apparent 
Diameter. 


Diameter in 
Miles. 


First, . . . 
Second, 
Third, . . 
Fourth, . . 


Id 18h 27m 33.5s 
3d 13h 13m 42s 
7d 3h 42m 33.4s 
16d 16h 32m 11.3s 


6.04S53 

9.62347 

• 15.35024 

26.99835 


1.015" 
0.911" 
1.488" 
1.273" 


2436 
2187 
3573 
3057 



218. Comets. — A mass of luminous matter, 
attended by a stream of light, is sometimes seen in 
the heavens. This is called a Comet, from the 
hair-like appearance of its train. Comets appear at 
very irregular intervals, with varying degrees of 
brilliancy, and are often seen outside the Zodiacal 
limits (Sec. 27) which include the orbits of all the 
larger planets, and of about two-thirds of the 
Planetoids (Sec. 214). For these reasons they 
have been regarded by some as the guerillas of the 
Universe, but it is known that they are subject to 
the laws which govern the motions of the plane- 
tary bodies, though astronomers have not been 



able to map out their orbits with the same pre- 
cision. 

The paths and periods of about 240 Comets 
have been computed, with greater or less accuracy, 
and it is estimated that several thousand of these 
objects come near enough to the Earth's orbit to 
be visible under favorable circumstances, their 
periods of appearance ranging from a i'ew months 
upwards, to hundreds of years. The total number 
circulating within the bounds of the Solar System 
is supposed to be more than three millions. 

210. Comets revolve around the Sun, in orbits 
of elliptic shape, — some of which are very much 



SATELLITES, AND COMETS. 



elongated, having one focus in, or near, the Sun, 
and the other many millions of miles distant. 
When in Perihelion (Sec. 1*77), the Comet is often 
a very brilliant object, and its train is many de- 
grees in length, spreading over a large part of the 
firmament. The Comet is then receiving so much 
light from the Sun as to become luminous, and 
moves very rapidly (Sec. 201). After having 
passed the Perihelion, the light received dimin- 
ishes, the train rapidly loses its brightness, and the 
angle under which it is seen from the Earth 
becomes smaller as the distance from the Sun 
increases, till at last the small portion of light 
reflected from the Comet is lost in the longer 
j)assage to the Earth, and the Comet is not again 
seen till, after having swept far out into sj>ace, it 
returns near the Earth's annual path. 

When in that part of the orbit nearest the Aphe- 
lion, the Comet moves much more slowly than 
when nearest to the Sun, the velocity being (Sec. 



201) inversely proportional to the Square of the 
Radius Vector; the Comet is, therefore, invisible 
during a great portion of the time occupied in 
each revolution. 

220. The first Comet of whose appearance 
we have any knowledge (January, A.D. C6), is 
remarkable, also, as having been the first to be 
identified as a member of the Great Solar Family ; 
this fact was ascertained by Dr. Halley soon after 
its re-appearance in 1862, and the Comet has, 
therefore, been named after him. It revolves 
about the Sun once in 76£ years. Its Perihelion 
distance is about 53,570,000 miles ; the distance 
at Aphelion is estimated to be 3,243,000,000 miles, 
or 500,000,000 miles outside the orbit of Neptune. 
The motion is retrograde (Sec. 152). The follow- 
ing shows the results of the observations made on 
the three last returns to the Perihelion ; the dis- 
tance at that point being compared with the Earth's 
mean Radius Vector as Unity : 



1759. 



1835. 



Date of Perihelion, 
Place of Perihelion, . 
Place of North Node, 
Inclination of Orbit, . 
Perihelion Distance, . 



Sept. 15 — 7 A. M. 

X? 1° 56 

» 21° 11 

17° 45 

0.5829 



March 13 — 1 A. M. 

fff 3° 10 

» 23° 50 

17° 37 

0.5845 



Nov. 16 — 10$ A. M. 

JX? 4° 32 
» 25° 10 

17° 45 

0.5866 



These observations show that the Longitude of 
the Perihelion and place of the Nodes, and the 
Perihelion distance, are constantly increasing. 
The elements of the orbit are computed from a 
series of observations taken before and after the 
Perihelion passage ; these give a portion of the 
curve, from which the whole is ascertained (Sec. 
199). 

221. Encke's Comet revolves in a compara- 
tively small orbit, in the short period of 3 years 
and 4 months. It was first seen in the year 1786, 
and the elements of the orbit were computed by 



Encke from observations on its Perihelion passage, 
January 27th, 1819. The Perihelion distance is 
about 31,000,000 miles, its place about 7° of Tl£. 
The Aphelion distance is 370,000,000 miles. 

Another Comet of short period, named after 
Biela — w ho determined its elements on the occa- 
sion of its Perihelion passage March 18th, 1826 — 
is chiefly remarkable as having excited fears of col- 
lision with the Earth during the present century. 
Its period is 2,460 days, or 6 years 9 months; the 
Perihelion distance is about 80,000,000 miles; the 
distance at Aphelion is 565,000,000 miles; its 



94 



ASTRONOMY. 



orbit very nearly touches that of the Earth in a 
point passed by the latter about the end of Novem- 
ber. This Comet was partially divided in Decem- 
ber, 1845, probably by collision with a stream of 
planetoids (Sec. 215.) 

222. The quantity of matter in a Comet is very 
small, as compared with the least of the planetary 
bodies; the fixed stars have often been seen 
through the most dense parts of the train, and the 
head, or nucleus itself, often appears to be little 
more than an aggregation of vapor. That a Comet 
has but little comparative weight, is also evident 
from the fact that when very near to a planet it has 
no appreciable power to turn that body from its nor- 
mal path (Sec. 204), while more than one instance 
has been noted in which the Comet has been turned 
aside by the attraction of the planet, and forced 
into a new orbit. 

Comets are, therefore, believed to be composed 
of matter in a state of great tenuity — volumes of 
gaseous substance, or small particles in a solid 
form, separated many miles from each other. In 
the latter case the character of the aggregation is 
identical with that of the Planetoid grouping (Sec. 
215), and it is thought probable that two Comets, 
— the third of 1862, and the first of 1866 — are 
comparatively dense portions of the two streams 
already mentioned, and revolve with them in 
periods of 121 years 6 months, and 33 years 2^ 
months. 

The other j>ortions of the Planetoidal stream, 
failing to reflect the light of the Sun, are necessa- 
rily much less dense than the Comet, containing 
even less matter than an equal bulk of our atmos- 
phere, and averaging but a few grains in weight to 
the cubic mile, though occasionally a compara- 
tively large mass may occur. Matter so very thin- 
ly spread out can exercise very little influence on 
a solid Planetary mass, and it is highly probable 
that if a Comet should come into direct " colli- 



sion" with the Earth, we should feel no more 
shock than if a large stone fell to the ground from 
a height of two or three hundred feet. 

223. aerolites. — When the Earth, in her an- 
nual journey, meets with a stream of Planetoids, 
those particles nearest to the Earth are drawn out 
of their course by her superior attraction, and fall 
to her surface. In passing through the atmos- 
phere they become heated by the friction of the 
air, and, abstracting oxygen from it, many of them 
burn with great rapidity. The larger masses fall, 
intact, to the ground, in which they are sometimes 
found imbedded to the depth of several feet. The 
smaller particles are burned up, and their ashes 
fall, more slowly, in the shape of minute atoms of 
dust. 

Few clear nights pass without the visible fall of 
many of these aerolites, and there is no reason to 
doubt that they fall as numerously during cloudy 
nights and in the day time. Sometimes they des- 
cend in showers, according as the particles met 
by the Earth are more or less numerous; the most 
brilliant displays occur in August and November 
(Sec. 215). The aerolites of August seem to spring 
chiefly from a point about 7 degrees South of 
Algol in Perseus ; those of November appear to 
radiate from a point near Algeiba in the Sickle of 
Leo. We estimate the thickness of the stream of 
Planetoids to be 50,000 miles (Sec. 215), for the 
reason that the aerolites continue to fall while the 
Earth passes over that distance in her orbit. 

This almost incessant fall of aerolites proves that, 
at least some, portions of what are usually called 
the "regions of space," are comparatively full of 
these floating particles, each of which is constantly 
in motion around some point as a center of revo- 
lution, just as the Moon moves around the Earth, 
and as both the E;irth and Moon perform an an- 
nual journey around the Sun. 



COMETS AND ZEOLITES. 



95 



224. It has been estimated that the number of 
aerolitic bodies falling towards the Earth, is about 
eight millions daily, possessing an aggregate 
weight of 1,000 pounds, or an average of a little 
less than a grain each. This is equal to an in- 
crease of the Earth r s mass to the extent of 180 
tons annually. About nine-tenths of this matter 
is supposed to descend to the ground, or the 
water, in the shape of dust (Sec. 223) ; the remain- 
ing one-tenth part retains the solid form on reach- 
ing the surface, the individual weight of these 
masses varying from a single ounce to more than 
17 tons. One of these bodies, weighing 700 
pounds, fell at Concord, Ohio, on May day, 1860, 
and another of 300 pounds weight fell at Weston, 
Connecticut, in Decembeiyl807. 

A total of eighteen solid aerolites are known to 
have fallen in the United States during the first sixty 
years of the present century, their aggregate 
weight being about 1,250 tons, and their average 
weight 3f times as great as that of an equal bulk 
of water; their specific gravity being thus some- 
wtiat greater than that of the Moon (Sec. 196). 



There is no reason to suppose that these averages 
will not hold good for the Planetoids falling over 
the whole extent of the Earth's surface. 

225. The fall of an aerolite has been witnessed 
on several occasions, and the body has been found, 
in every case, to be very hot. On being subjected 
to chemical analysis they all prove to be composed 
of substances identical with those called chemical 
elements, the combinations of which make up the 
sum total of all the various forms of matter within 
our reach. Some of them contain a large propor- 
tion of iron, copper, nickel, tin, sulphur, phospho- 
rus, oxygen, and the components of salt, clay, 
flint, lime, potash, and coal. None have yet been 
ascertained to contain any element not already 
known, though all, without exception, contain a 
compound of iron, nickel, and phosphorus, called 
Schreibersite, which has never been met with, as a 
compound, except in aerolites. Some of those 
which are principally composed of the least cohe- 
sive substances are broken up by the heat produced 
in the fall through the atmosphere, and reach the 
ground in fragments. 



Define i 



) explain (the f 



s refer to the sections) : 



214. Planetoids ; when discovered ; number ; peculiarities ; rings of Planetoids ; Saturn's ring. 215. Elements of 
Ceres, Pallas, Juno, and Vesta. 216. Satellites. 217. Moons of Jupiter. 218. Comets; appearance; movements; num- 
ber known; number in the System. 219. Orbit of Comet ; relative motion. 220. Halley's Comet. 221. Encke's and 
Biela's. 222. Matter iu a Comet ; consequences of a collision with the Earth. 223. ^Erolites ; number ; displays of 
August and November. 224. Weight of serolites. 225. Chemical analysis. 



THE FIXED STARS. 



226. The attempt to ascertain the distances 
and bnlks of the Fixed Stars, has not hitherto been 
so successful as in the case of the principal mem- 
bers of the Solar family. We can calculate our 
relative distance from a planet, as Jupiter, (Sec. 
203) — but a journey round the whole circumference 
of the Earth's orbit furnishes us with no two posi- 
tions in which there is a measurable change in the 
apparent magnitude of a fixed star, and only gives 
a barely appreciable difference of place in the case 
of a very i'^w stars. 

Careful observations of Sirins — one of the 
brightest of the starry host — (Sec. 79) haA*e ena- 
bled astronomers to detect a slight difference in his 
apparent declination, as seen from opposite sides 
of the Earth's orbit, equal to a parallax (Sec. 177) 
of about one second and a quarter, taking the 
Earth's mean distance from the Sun as a base 
line ; this angle is less than one-seventh part of the 
Solar Parallax, the base line of which is the Earth's 
radius. The distance of Sirius from the center of 
the Solar System, as computed from this parallac- 
tic angle (Sec. 194) is something more than fifteen 
millions of millions of miles. a Centauri is sup- 
posed to be the nearest star to our Sim. 

If we should assume that the fixed stars are all 
of equal bulk, it would follow that those of lesser 
apparent magnitude must be much farther distant. 
It is, however, probable that the stars differ as 
much in actual size and weight, as do the heavenly 
bodies whose bulks have been measured, but it is 
also probable that some of the largest are among 
those of small apparent magnitude, and it has 
been estimated that Sirius, and a few other Stars 



which have been found to show a small parallactic 
angle, are as much nearer to us than a multitude 
of stars which have no parallax, as is the Moon 
compared with Xeptune. 

It has been thought that some of the more dis- 
tant of those stars visible to the naked eye are at 
least sixty times farther removed than Sirius from 
the Sun. Even these remote bodies do not lie near 
the boundaries of the Universe. The cloud-like 
nebulae in Cancer, and Andromeda, and Orion, 
which are visible at times to the naked eye ; the 
shining Milky Way which encircles the heavens, 
and thousands of other luminous groupings, have 
been looked at through the telescope, and seen to 
consist of distinct Stars, only shut out. by their 
remoteness, from the unaided vision. 

It is probable that if we could stand on one of 
those most distant Stars, and look out farther 
away from the Sun. we should still find the view 
bounded only by our ability to peer into the ini-. 
mensity of space. We conclude that the Universe 
is infinite in extent ; without bounds. We may not 
be able to grasp the full meaning of this state- 
ment, but there is no more difficulty in believing it 
than in trying to think of a vast space with 
unknown limits, and the inevitable something be- 
yond. 

227. The number of fixed stars discernible 
with the naked eye, is about three thousand. Of 
these 19 are of the first magnitude ; 3 between the 
first and second; 31 of the second; 2-5 between 
the second and third; 116 of the third; and 73 
between the third and fourth. On the preceding 
maps they are represented as being 22 of the first, 



THE FIXED STARS. 



56 of the second, and 189 of the third. The num- 
bers classed under each successive magnitude in- 
crease rapidly, and when the telescope is employed 
the Stars may be counted by millions, spaces be- 
ing found to be thick with Stars, which were mere 
blanks to the naked eye. The number seen ap- 
pears to be limited only by the power of the instru- 
ment used. "We conclude that the Stars are 
infinite in number, like the extent of the space 
they occupy. 

228. The Fixed Stars could not be visible to 
us at such immense distances (Sec. 226), even as 
luminous specks, without having great actual mag- 
nitude, and shining with their own light, like the 
Sun. The Planet Jupiter is 88,316 miles in diam- 
eter, and yet, at his mean distance from the Earth, 
he is not much brighter than Sirius, though 
30,000 times nearer. 

Light reflected from a body a thousand times 
larger than Jupiter, would be lost long before 
reaching us from the distance of Sirius. The light 
we receive from Sirius has been estimated at one 
part in 20,000,000,000 of that received from the 
Sun, but. as the intensity of light diminishes — like 
the attraction of gravitation — with the square of 
the distance, the diameter of Sirius must be twice 
as great, or the intensity of light from an equal 
area of surface must be four times as great, as that 
of the Sun, in order to produce this result. Hence 
we conclude that some of the fixed stars are at least 
as large as our Sun, and that, like him, they shine 
with then- own light. 

229. Many stars appear to be double; and 
there are few of the larger magnitudes but have a 
companion, in some cases so small, or so distant, 
as to be visible only with the aid of a good tele- 
scope. There is no doubt that in many of these 
instances the apparent companionship is simply an 
accident of position, the smaller star being many 
millions of miles farther away from us than its 



more illustrious neighbor, but nearly on the same 
line of vision. 

There are, however, many well known cases of 
two, three, four, or more stars, forming a separate 
system. The Stars composing one of these sys- 
tems are observed to approach and recede from 
each other, changing their relative positions with 
a regularity which leaves no room to doubt that 
they revolve around a common center of gravity, 
as is the case with the Earth and Moon (Sec. 196). 

230. The annual variations in the Eight Ascen- 
sion and Xorth Polar Distance, given in our table 
of Fixed Stars, are principally the equivalents of 
the precession in Longitude (Sec. 208), but they 
also include another element — an individual mo- 
tion — a relative change of place, in many of the 

! fixed stars. Most of the Stars which have been 
watched for a long time are found to be affected 
with this "proper" motion. 

Seasoning from an analogy which has a wide 
spread basis, we find no room to doubt that every 
Star in the Universe is in motion around some 
central point or body. We conclude that motion 
is the condition of existence. Gravitation is the 
law of matter (Sec. 202), and motion is the expo- 
nent of its all-pervading power. The word 
"fixed," as applied to the Stars, is, therefore, to 
be understood in a comparative sense only, the 
apparent changes in the angular positions of the 
Stars, with regard to each other, being very small 
as compared with those of the planetary bodies. 

231. Changes in the apparent magnitude of 
Stars are numerous. Mira, in Cetus, is remarka- 
ble as varying from the second magnitude to the 
seventh, with a period of about eleven months. 
Algol, in Perseus, has a shorter period of a little 
less than three days, during which it varies be- 
tween the second and fourth magnitudes. Sheliak, 
in Lyra, has a periodical change in apparent 
brightness of about six days and a half 



ASTKONOMY. 



From these, and numerous other cases of varia- 
tion, we conclude that all the Stars rotate on their 
own axes, as is the case with every member of the 
Solar System (Sec. 192), and that some portions 
of the surface of a variable Star are less luminous 
than others, the brighter side being turned towards 
us when the magnitude appears to be greatest. 
It is, however, possible that the dimness may be 
caused, in some cases, by the passage of a planet, 
or belt of Planetoids, between us and the Star. 

It is thought probable that each of these Stars 
is a Sun like our own (Sec. 228), and gives light 
to a family of planetary worlds, which shine with 
a reflected light only, and are, therefore, invisible 
to us at such immense distances. To the inhabi- 
tants of those worlds our Sun would appear but 
as a fixed star, and his large train of planetary 
attendants remain forever unknown. 

232. Sinus is usually described as a brilliant 
white star (Sec. 79), but was referred to by the an- 
cients as of a fiery red ; it is now assuming a green 
color. Capella was also a red star formerly, af- 
terwards yellow, and is now white (Sec. 68) but is 
gradually assuming a blue tinge. These, and 
other, variations in color warrant the inference 
that extensive changes are in progress. Several 
instances are on record of stars which suddenly 
appeared in the firmament, and after shining for a 
brief period, with rapid changes of color, have 
disappeared with equal suddenness, and left no 
traces of their existence. 

The Star r h in the stern line of Argo, has recently 
diminished very much in apparent brilliancy, while 
a nebula surrounding it has correspondingly in- 
creased in brightness, and also undergone a marked 



change in form. The nebula is apparently grow- 
ing richer at the expense of the Star. This is a 
very singular phenomenon ; it is not only without 
a known parallel, but it indicates a process directly 
the reverse of that by which our Earth and Sun 
are continually receiving additions to their masses 
from the falling aerolites (Sec. 224). 

233. The chemical analysis of the Planetoids 
which have fallen to the Earth's surface shows that 
of the sixty-three substances, called elements, of 
which the material of our Earth is composed, 
about twenty-two have been found in the aerolites, 
while no element has been found in their analysis, 
which was not previously known to the chemist 
(Sec. 225). This fact has been accepted as an 
argument in favor of the theory that all the Planets 
and Planetoids were formed from the same mate- 
rial as our Earth, though these elements may enter 
into different combinations, resulting in distinct 
forms of material existence, in the case of each 
body in the Solar System. Recent experiments, 
by which the light of the Sun has been compared 
with that arising from the burning of a large num- 
ber of earthly substances, seem to warrant the 
conclusion that the Solar body is composed of the 
same chemical elements as those which enter into 
the composition of the bodies revolving around 
him. There are, also, good reasons (Sees. 228 and 
231) for believing that the Sun and Fixed Stars 
are alike in character and function. Hence it is 
considered to be highly probable that the whole 
Universe of Stars and Suns, Planets, Satellites, 
Planetoids and Comets, was originally formed 
from the same elements — individualized out of a 
primeval chaos. 



Define and explain (the figures refer to the sections) : 

226. Fixed Stars ; Parallax and distance of Sirius ; relative distances ; visible nebulas ; extent of the Universe. 227. 
Number of Fixed Stars. 228. Actual magnitudes; light. 229. Double Stars; relative motion. 230. Proper motion; 
meaning of the phrase " Fixed Star." 231. Rotations on Axis ; Planetary systems. 232. Changes in color ; disappear- 
ance. 233. All composed of like material ; Experiments on Sunlight, 



THE SUN'S MOTION. 



234. The Stars in the vicinity of the constella- 
tion Hercules, are apparently farther apart now 
than at the beginning of the present century. 
Such a systematic widening could scarcely result 
from any other cause than a gradual lessening of 
the distance between us and the Stars in that part 
of the heavens (Sec. 199), and it is inferred from 
this that the Sun is moving towards that constella- 
tion at the rate of about 120,000 miles per hour, 
or nearly 3,000,000 miles per day, or almost twice 
the distance that the Earth travels in her orbit in 
the same time. 

As every other body appears to move in a curve, 
it is reasonable to suppose that this motion of the 
Sun is in an elliptic orbit, and it has been boldly 
guessed that the center of this orbit is Alcyone, 
the brightest star in the Pleiades of Taurus, which 
is assumed to be 34,000,000 times as far from the 
Sun as the Sun is distant from the Earth. The 
Sun is supposed to require about 18,200,000 years 
for one revolution, and the plane of the orbit to be 
inclined 84 degrees to the plane of the Ecliptic, 
the two planes being nearly perpendicular to each 
other, and intersecting in 22° of tf and m,. 

235. The direction of the Sun's motion is thus 
nearly in the direction of the North Pole of the 
Ecliptic, and nearly perpendicular to the plane of 
the Earth's annual revolution. Owing to the great 
size of the Sun's Orbit, his course can vary but 
little from a straight line in several centuries. 

The absolute motion of the Earth in space is, 
therefore, like the movement up a spiral staircase, 
and will be best understood by supposing the table 
(Sec. 13) to be raised through a space equal to 



about six times its diameter, while the ball and wire 
are being carried once round the edge of the table. 
The radius of the Earth's Orbit (01,328,000 miles) 
x 2 x 3.14159, gives the circumference of the 
orbit, which, divided by the number of hours in a 
year, gives 65,460 miles per hour as the Earth's, 
mean motion. A similar computation for the Sun 
will give his hourly motion as 122,260 miles. But 
these quantities represent the two legs of a right; 
angled triangle, and the square root of the Sum of 
their squares represents the hypothenuse, equal to 
138,700 miles, which is the absolute hourly motion 
of the Earth in space — being nearly twice as great 
as her motion in the orbit would be if the Sun 
were stationary. 

The annual forward -motion of the Sun is 11.74 
times his mean distance from the Earth, and her 
real path may, therefore, be approximately repre- 
sented by a string wound spirally round a cylin- 
der, in such a way that the distance between the 
turns of the string is nearly six times the diameter 
of the cylinder. 

If the direction of the Sun's motion were ex- 
actly perpendicular to the plane of the Ecliptic a 
line parallel to it, and passing through the Earth, 
would always make an angle of about 28° 10 with 
the line of the Earth's absolute motion ; but this 
angle is subject to a slight variation, and the Earth's 
motion is also variable, because, owing to the slight 
obliqueness of the grand axis, her Radius Vector 
(Sec. 199) is, twice in each year, 6° out of the per- 
pendicular to the axis. 

236. The mean distance of the Moon from the 
center of gravity, which moves equably round the 



100 



ASTKONOMY. 



Sun (Sec. 196), is about 235,000 miles, which is, 
therefore, the mean length of her Radius of Revo- 
lution. The Moon's Sidereal Period being 27.32166 
days, the mean hourly motion in her orbit would 
be 2,250 miles, if the center of her orbit were sta- 
tionary. But it is evident that the actual motion 
is much greater, as, during each hour, the Moon 
moves through a distance of 138,700 miles in 
space, in company with the Earth (Sec. 235). It 
is also apparent that her absolute motion is in a 
curve which differs but little from that traversed 
by the Earth, though relatively she revolves round 
a point within the Earth's mass. 

Let us suppose the Earth to be represented by a 
marble, moving along the middle of a race course 
one mile in circumference, and the Moon at Full 
represented by a small pea placed two feet from the 
marble towards the outside of the track ; remove 
the marble 35 yards along the track, placing the 
pea two feet in advance, on the same line, and the 
two will represent the positions at the Moon's third 
quarter ; remove the marble 35 yards still farther, 
placing the pea two feet distant towards the in- 
side of the track, to represent the position of the 
New Moon ; the process continued will give the 
relative positions for the first quarter, and the 
Full Moon. 

A line traced through the points successively 
occupied by the pea, while the marble is carried 
140 yards along the track, will represent the actual 



path of the Moon in the heavens during one Luna- 
tion, while an orange moving more slowly in an 
arc half way between the track and the center of 
the field, will nearly represent the relative motion 
of the Sun with regard to the Earth and the Moon, 
though not with reference to the centre of his own 
orbit. It is apparent that the path of the Moon 
in space is never convex towards the Sun. 

237. The relative motions of all the planetary 
bodies in space can not be represented by a dia- 
gram, but we can form some idea of the great 
movement if we conceive a number of concentric 
cylinders, the diameters of which are proportional 
to the distances of the planets from the Sun, and 
suppose that the rate of motion parallel to the axis 
of the cylinders is the same in each case (subject 
to the irregularity due to the fact that the planes 
of their orbits do not exactly coincide with each 
other, or with the plane of the Ecliptic), while the 
angular motions around the common axis of the 
cylinders are unequal, being proportional to the 
times of revolution of the bodies around the Sun 
(Sec. 213). If with this we can also grasp the 
idea of satellites revolving around some of the 
planets, and comets and streams of Planetoids 
revolving in more elliptic orbits about the ever 
progressing point in the axial line, we shall be able 
to comprehend, though faintly, the motion of the 
Solar system as a whole. 



Define and explain (the figures refer to the sections) : 
234. Absolute motion ; Orbit of the Sun. 235. Motion of the Earth i: 
tion. 237. Relative movements of members of the Solar System. 



space ; illustration. 



. Moon's actual mo- 



INDEX. 



[The numbers refer to the pages, not to the sections.] 



Aehernar (in Eridanus) ; 21, 46. 

Acubens ; 26, 29, 48. 

Adhara (in Canis Major); 26, 47. 

Aerolites ; 94 

Asrena ; 43, 44, 49. 

Albireo (in Cygnus) ; 38, 43, 52. 

Alchiba ; 31, 48. 

Alcor; 28. 

Alcyone (in Pleiades); 22,46. 

All'ebiran (in Hvades); 22,46,57,59. 

Alderamin ; 15, 43, 52. 

Aldhafara (in Sickle) ; 29, 48. 

Alga; 34, 51. 

Algedi; 36. 

Al-eibi; 29, 48. 

Algenib ; 17, 21, 38, 43, 45. 

Algol ; 18, 22, 46, 97. 

Algorab (in Corvus) ; 31, 49. 

Allieua; 25, 47. 

Alioth ; 13, 28, 49. 

Alkaid ; 13, 28, 39, 49. 

Alkaturgos ; 39, 50. 

Alkes; 31, 48. 

Almiach; 17, 18,46. 

Alnilaui (Belt Orion) ; 23, 47. 

Alnitak do. ; 23,47. 

AlphuM (Cor. Hvdra?); 26, 31, 41, 48. 

Alpbecca; 39, 40, 50. 

Alpheratz; 17, 18, 37,38,45. 

Alpliirk; 15, 52. 

Ah'u -cibah (Pole Star) ; 13, 45, 53. 

Alshaiu (in Aquila) ; 35, 52. 

Altair ; 35, 52. 

Altar (see Ara). 

Aludra ; 26, 41, 47. 

Ahvaid; 15, 51. 

American Goose ; 53. 

Andromeda ; 17, 18. 

Angular Measures ; 9, 10, 13, 17, 73. 

Annual Motion ; 6, 7, 8. 

Variation ; 45 to 53, 90. 
Annular Eclipse ; 75. 
Anser; 42, 43, 52. 
Antarctic Circle ; 42. 
An tares ; 32, 33, 50. 
Antinous et Aquila ; 35, 37, 42. 
Aphelion ; 73. 
Apogee ; 73. 
Aquaries ; 9, 37, 38. 
Aquila ; 35, 36, 37, 42. 
Ara ; 32, 33, 34, 36, 42, 44. 



Archer (see Sagittarius). 

Arcturus ; 30, 39, 49. 

Argo ; 27, 41, 42, 44. 

Aries ; 9, 17, 19, 20, 22. 

Arista ; 30, 39, 49. 

Arneb ; 26, 47. 

Arrow (see Sagitta). 

Ascensional Difference ; 55, 56, 59. 

Ascension (see Riijht Ascension). 

Aselli (in Cancer) ; 26, 48. 

Asterion ; 28, 39. 

Attraction of Gravitation ; 84. 

Attraction — Tides; 87. 

Aurisia ; 23, 25, 42. 

Azha (in Eridanus) ; 21, 46. 



Balance (see Libra). 
Baton Kaitos ; 21, 46. 
Bear Driver (see Bootes). 
Bears and the Pole ; 16. 
Beehive Nebula (see Prasepe). 
Bellatrix (in Orion) ; 23, 46. 
Ikiicinasch (see Alkaid) 
IJctcl-ucuse ; 23, 25,47. 
Biela's Comet; 93. 
Bootes ; 28, 30, 39. 
Bull (see Taurus). 
Bull's Eye (see Aldebaran). 

" North Horn (see El Nath). 



Camelopardalus ; 18, 27. 
Cancer ; 9, 26. 
Canes Ycnatici ; 28, 39. 
Canis Major ; 25, 26, 41. 

" Minor; 26. 
Canopus ; 24, 41, 47. 
Capclla; 23,46. 
Capricornus ; 9, 36, 37. 
Caput (Head) Medusae ; 22. 
Cassiopeia ; 14, 17, 18. 
Castor; 25, 47. 
Celbelrai ; 34, 51. 
Centaurus ; 31, 32, 33, 42, 44. 
Cepheus; 15, 18,43. 
Cerberus ; 39. 
Ceres; 91. 
Cetus ; 19, 20, 38. 



Chameleon ; 42. 

Chair; 14. 

Chaph; 14, 45. 

Chara ; 28, 39. 

Charles' Oak (see Robur Caroli). 

Chronology; 76. 

Circinus; 34, 42. 

Clypei Sobieski ; 35. 

Collision with a Comet; 94. 

Columba Noachi, 27. 

Colure ; 13, 14, 15. 

Coma Berenices ; 31. 

Comets; 92. 

Compasses (see Circinus). 

Conjunction, Inferior; 65. 

Superior ; 63, 65. 
Constellations; 10. 
Cor Caroli ; 28, 30, 39, 49. 

" Leonis ; 28, 48. 
Corona Australis ; 36. 

Borealis ; 34, 39. 
Cor Scorpii ; 33, 50. 
Corvus; 31. 
Crab (see Cancer). 
Crane (see Grus). 
Crater ; 29, 31. 
Crow (see Corvus). 
Crux ; 42, 44. 
Culmination ; 11, 54, 60.- 
Cup (see Crater). 
Cursa ; 24, 46. 
Cycles ; 76, 77, 78. 
Cygnus ; 15, 16, 38, 43. 



Dabih ; 36, 52. 

Day, Lenuth of; 55, 59. 

" Sidereal; 6. 
Declination ; 8, 53, 54, 57, 58. 
Delphinus ; 35, 37, 
Deneb ; 16, 43, 52. 
Deneb El Okab (in Aquila) ; 51. 
Denebola ; 29, 48. 
Density of Comets ; 94. 
" Earth ; 80. 
" Moon ; 81. 
" " Planetoids; 94. 
" " Sun and Planets ; 90. 
Deshabeh ; 36, 52. 
Diagram, Diurnal Motion ; 55. 
" Earth's Motion ; 7. 



Diagram, Earth's Orbit ; 83. 
" Horizon Circles; 61. 
" Jupiter's Motion ; 64. 
" Lunar Motion ; 72. 
" Mercury's Orbit ; 66. 
" Moon's Distance; 80. 
" Nutation and Precession ; ! 
" Transit of Venus; 82. 
Venus' Orbit ; 66. 
Diameter of Earth; 5, 79. 
" Moon ; 80, 90. 
" " Planets ; 85, 90. 

" Sun ; 82, 90. 
Diamond of Virgo ; 30. 
Dionvsian Period ; 78. 
Diph'da ; 21, 45. 
Dipper ; 13, 28, 39. 
Distance (if Moon ; 80. 
" Sun; 81,89. 
" Venus ; 81. 
North Polar ; 8, 45, 53. 
Diurnal Arc ; 55, 59. 

" Motion ; 5, 7, 54, 55. 
Dog, Greater (see Canis Major). 
" Lesser (see Canis Minor). 
Dog Star (Sinus); 26. 
Dolphin (sec Delphinus). 
Dominical Letter ; 77. 
Doradus ; 24, 42, 46. 
Dorsa Leonis ; 29. 
Dove (see Columba). 
Draco ; 14, 15, 39. 
Dragon (see Draco). 
Dubhe ; 13, 28, 48. 



Eagle (see Aqnila). 

Earth's Annual Motion ; 6, 7. 

" Axis ; 6, 7. 

" Diurnal .Motion ; 5, 54, 55. 

" Motion in Orbit; 83. 

" Motion in Space ; 99. 

" Size ; 79. 

" Weight; 80. 
Easter ; 78. 
Eclipses; 72. 
Ecliptic; 7, 9. 
Elongation ; 65, 67. 
El Natli; 23,46. 
El Fheckra; 48. 
El Rischa ; 18, 19, 46. 
Encke's Comet ; 93. 
En if; 38, 52. 
Epact; 78. 

Equal Areas in Equal Times; 83. 
Equation of Time; 8, 12. 
Equator ; 6. 
Equinoctial ;.6, 54. 
Equinoctial Colure; 13, 14, 17, 30, 44. 
Equinoxes; 7, 8, 9, 16. 
Equ ulcus; 38. 



Eridanus; 21, 22. 
Er Kai ; 15, 53. 
Er Raids ; 15. 
Etanin ; 15, 51. 
Evening Star ; 65. 



Falling to the Sun ; 84. 

Fishes (see Pisces). 

Fish, Southern (see Piscis Australis). 

" Flying (see Piscis Volans). 
Fixed S'tars; 5, 45 to 53. 

Changes ; 97, 98. 
" Distances; 96. 
" Light; 97. 
" Number ; 97. 
" Parallax; 96. 
" Proper Motion ; 97. 
e Musca). 



Fly (se 
Flying 1 
Fomalha 



G. 

Gemini ; 9, 23, 25. 

Geocentric Position ; 65. 

Giansar (in Draco); 48. 

Gienah ; 38, 43, 52. 

Gleaner (see Virgo). 

Goat (see Capricornus). 

Golden Number ; 78. 

Gomeisa ; 26, 47. 

Goose (see u Tueanas) ; 53. 

Graffias ; 33, 50. 

Great Bear (see Ursa Major). 

Greek Alphabet; 11. 

Gruinium ; 15, 51. 

Grus ; 36, 37. 



H. 

Halley's Comet ; 93. 
Hamal ; 17, 19, 46. 
Hare (see Lepus). 
Harp (see Lyra). 
Heliocentric Position; 65. 
Hercules ; 39, 99. 
Homan ; 38, 53. 
Horizon ; 8, 60, 61. 
Hunter (see Orion). 
Hyades; 22, 23. 
Hydra ; 28, 29, 31, 33. 
Hydrus ; 24, 43. 



J. 

Julian Period ; 78. 
Juno; 91. 
Jupiter; 62. 

" Elements ; 89, 90. 

" Longitudes ; 63. 

" Moons ; 92. 



Kaus Australis; 51. 
Kochab; 14,49. 
Koi'iieforos ; 39, 50. 



Lacerta ; 18, 43. 
Lady in Chair (se 
Latitude; 8, 58. 

of Earth; 87. 
" Moon ; 72. 
" Stars ; 45 to 53. 
Law of Attraction ; 84. 

" " Motion in the Orbit; 8; 
Leap Year ; 76. 
Leo; 9,26,28,29. 

" Minor ; 29. 
Length of Day ; 8, 54, 55, 57. 
Lepus ; 25, 26. 
Lesath ; 33, 51. 
Libra ; 9, 32. 
Lion (see Leo). 

Lesser Bear (see Ursa Minor). 
Lizard (see Lacerta). 
Longitude; 8, 58. 

of Jupiter; 63. 
" " Mars; 68. 

" " Mercury; 67. 

" " Neptune; 70. 

" " Saturn ; 69. 

" " Stars ; 45 to 53. 

" Sun : 11, 12. 
" " Uranus ; 70. 

" Venus; 66. 
Lunar Cycle ; 76. 
Lunation ; 71. 
Lupus ; 32, 34, 44. 
Lynx; 27,29. 
Lyra; 40. 



M. 

Magnitudes of Planets; 90. 

" Stars ; 10, 97. 
Map I. ; 14. 

" II. ; 18. 

" III. ; 21. 

" IV. ; 23. 

« V. ; 26. 



103 



Map VI. ; 29. 

" VII. ; 30. 

" VIII. ; 33. 

" IX. ; 35. 

" X. ; 37. 

" XI. ; 39. 

" XII. ; 41. 

" XIII. ; 43. 

" XIV. ; 60. 
Mars ; 63, 89, 90. 
Murkab; IT, 53. 
Matar ; 38, 53. 

Matter, the same in all ; 95, 98. 
Measure of Angles ; 9, 10, 13, 17, 73. 
" " Attraction ; 84. 
" " Distance ; 73, 79. 
Measures of Time ; 76. 
Measure of Weight; 80. 
Mebsuta ; 25, 47. 
Megrez ; 13, 17, 28, 49. 
Me'nkalinan ; 23, 25, 47. 
Menkar ; 20, 21, 46. 
Merak; 13,28,48. 
Mercury ; 67, 89, 90. 
Meridian ; 6,60. 
Mesarlliim ; 19. 
Meteors ; 94. 
Metonic Cycle; 78. 
Microsropium; 36,37. 
Milky Way ; 10, 14, 15, 18, 22, 24, 27, 

34, 36, 38, 40, 42, 43, 44. 
Mintaka (Belt Orion) ; 23, 47. 
Mira; 17, 18, 20, 21,46,97. 
Mir.iHi; 17,45. 
Mirfak ; IT, 18, 22, 46,97. 
Mirzam ; 26, 47. 
Mizar ; 13, 28, 49. 
Monoceros ; 23, 27. 
Mons Mensa ; 42. 
Moon; 71. 

Moon's Age ; 78. [90. 

i'< inner Si: e and Weight; 80, 
Real Path ; 100. 
Moons of Jupiter ; 92. 
Mouth; 77. 
Morning Star ; 65. 
Motion in Orbit; 62, 83. 

" of Stars ; 5 to 11, 13, 16, 97. 
" " Systems ; 97, 99. 
Muliphen ; 26. 
Muphrid; 39, 49. 
Musca; 19, 32, 42. 
Mutual Attraction ; 85. 



N. 

Naos; 41, 47. 

Nebube; 10, 18, 23,26, 47, { 
Nekkar ; 16, 39, 50. 
Neptune ; 70, 89, 90. 
Net (see Reticulum). 
Nibal ; 26. 



Nodes of Moon; 71,86. 
Norma Euclidis ; 34. 
North Asellus ; 26, 48. 
North Polar Distance; 
Nutation ; 85. 



Octans; 42. 
Oculus Pavonis; 
Ophiucus ; 32, 33 
Opposition ; 63. 
Orion ; 23, 25. 



Painter's Easel (see Pictoris). 

Pallas; 91. 

Parallax; 73. 

Pavo ; 36, 42. 

Peacock (see Pavo). 

Pegasus; 17, 18,20,38,43. 

Penumbra; 74. 

Perigee; 73. 

Perihelion; 73. 

Perseus ; 18, 22. 

Phact ; 27, 47. 

Phecda ; 13, 28, 48. 

Phoenix; 21. 

Phurid (in Canis Major) ; 47. 

Pictoris ; 42. 

Pisces ; 9, 18, 20, 38. 

Piscis Australis ; 38. 

" Volans ; 42. 
Planetoids; 91. 
Planets; 62, 89,90, 100. 
Pleiades ; 22, 46 (Alcyone). 
Pointers; 13. 
Points of Compass ; 11. 
Poles of the Heavens ; 6, 15. 
Pole Star; 5, 13,14,45. 
Pollux; 25,47. 

Precession of Equinoxes; 9, 16,85,87. 
Prime Vertical ; 60. 
Procyon ; 26, 47. 
Propus ; 25. 



Radius Vector ; 83. 
Ram (see Aries). 
Rasalague ; 34, 40, 51. 
Rasal Asad (in Leo) ; 48. 
Has Algethi; 34,40, 51. 
Rastaban (see Alwaid). 
Ratio of Distance ; 84, 89, 90. 
Refraction ; 54, 55, 57. 
Regtllus; 28, 48. 
Reticulum Rhomboidalis; 24. 
62. 



Rigel ; 23, 24, 46. 

Right Ascension ; 8, 10, 45 to 53, 57, 58. 

of Stars ; 45 to 53. 

" Sun ; 11, 12, 57. 
Rising ; 54, 59, 60, 61. 
River (see Eridanus). 
Robur Caroli ; 41. 
Roman Infliction ; 78. 
Rotanen; 35, 52. 
Ruchbah ; 45. 
Ruchban Ur Ramih ; 52. 



Sadalmelik ; 37, 53. 
Sadalsund ; 37, 52. 
Sadr ; 43, 52. 

Saiph ; 23, 47. 
Sagitta; 43, 52. 
Sagittarius; 9, 35. 

Satellites; 92. 

Saturn ; 69, 89, 90. 
Scales (see Libra). 
Scheat Aquarii ; 37, 53. 
" Pegasi ; 17, 53. 
Schcdir ; 14, 45. 
Scorpio ; 9, 32, 33, 35. 



Seeumla. Giedi ; 36, 52. 

Seginus ; 49. 

Semi-Diameter ; 73, 79. 

Semi-Diurnal Arc ; 55. 57, 59. 

Serpens ; 33. 35, 39. 

Serpen tarius (see Ophiucus). 

Serpent Bearer (see Ophiucus). 

Setting ; 54, 59, 60, 61. 

Shape of the Karth ; 79. 

Sheliak ; 40, 51. 

Sheratan ; 19, 46. 

Ship (see Argo). 

Sickle of Leo ; 29. 

Sidereal Day ; 6. 

" Revolution ; 63, 89. 
" Time; 10, 11. 
Signs of Zodiac; 9, 10. 
Sirius; 26, 47. 
Snake (see Hydra). 
Solar Cycle; 77. 

" Day; 6. 

" System ; 62 to 95. 
Solar Motion in Space; 99. 
Solstitial Colure; 15, 35, 40. 
South Asellus ; 26, 48. 
Sonth'n Crown (see Corona Australis). 
Southern Fly (see Musca). 
Southing ; 11, 54, 60. 
Spica Virginia ; 30, 49. 
Square of Pegasus; 17, 18,20, 38. 
Squaresof Times proportional toCubes 

of Distances; 85. 
Sulaphat ; 40, 51. 
Sunday; 77. 



104 



Sun's Densitv ; 82, 90. 

" Diameter ; 57, s->, 90. 

" Distance ; 81, 89. 

" Light; 98. 

" Orbit ; 99. 

" Semi-Diameter; 73,82 

" Parallax ; 73, 81. 

" Weight ; 82, 90. 
Svalocin ; 35, 52. 
Swan (see Cygnus). 
Synodical Revolution ; 63. 



Declinations ; 58. 

Elements of Solar Svste: 

Equation of Time; 12. 

Fixed Stars ; 45 to 53. 

Jupiter's Places; 63. 

Satellites; 92. 

Mars' " 68. 

Mercury's " 67. 

Moon's Elements ; 90. 

Neptune's Places ; 70. 

Planetoids ; 91. 

Eefraction ; 57. 

Right Ascension ; 58. 

Saturn's Places; 69. 

Sun's " 12, 

Uranus' " 70. 

Yenus' " 66. 
Talita ; 28, 48. 
Tarazed (in Aquila) ; 52. 



[90. 



Taurus ; 9, 22. 

Taurus Poniatowski ; 32, 34, 35. 

Tejat ; 25, 47. 

Telescopium ; 23, 25, 32, 33, 36. 

Theemin; 21, 46. 

Thuban ; 15, 49. 

Tides; 87. 

Toucan ; 53. 

Transit of Yenus; 66,81. 

Triangulum; 18,19. 

Triangulum Australis ; 33, 42, 44. 

Tureil; 27, 41,47. 



Umbra; 74 

Unicorn (see Monoceros). 
Unsrula ; 42, 44, 49. 
Unukulhay ; 33, 50. 
Uranus: 69, 89,90. 
Urkab Ur Ramih ; 52. 
Urn of Aquarius ; 37. 
Ursa Major ; 13, 28. 
" Minor; 14. 



V. 

Yega ; 40, 51. 
Yenus ; 65, 89, 90. 

" Distance; 81. 

" Transit of; 66, 81. 
Yernal Equinox ; 8, 13, 14, 17. 
Yesta; 91. 
Yirgin (see Yirgo). 



Yirgo; 9, 29, 30. 
Yindemiatrix ; 30, 49. 
Yulpecula et Anser ; 43. 

W. 

"Water Bearer (see Aquarius). 

Water Snake (see Hydrus). 

Wagoner (see Auriga). 

Wasat: 25,47. 

Week; 77. 

Weight of Earth ; 80, 90. 

" Moon and Sun ; 80, 82, 90. 

" Planets; 90. 
Wesen ; 26. 47. 
Whale (see Cetus). 
Winged Horse (see Pegasus). 
Wolf (see Lupus). 



Zaurak ; 21, 46. 
Zaviiava ; 29, 30,48 
Zenith ; 11. 60. 
Zodiac: 9. 10, 20. 
Zozma ; 29, 48. 
Zuh.-nels; 32, 50. 
Zubenesch; 32,49, 



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